PhotoFreebies 
... is a collection of free plugins for performing usefull photo manipulations and effects e.g. sepia effects, desaturation gradients, b/w conversion, color space transformations and many more.

Plugin Galaxy  
... is a set of 20 plugins with all kind of fantastic effects. Two of these plugins (PopArt and Zoom) are free!

Harry's Filters 
... contains 55 filter effects. They include filters for changing the image color or mood, for creating artistic effects, producing colorful gradients or impressive patterns, warping images, adding special noise effects to images, encrypting and decrypting images with 64 bit keys and producing various other effects like zoom, mirror or paint effects.

HyperTyle  
... is a plugin for generating texture, surface, paint, erosion, transparency, edge, frame and shadow effects. There is a Freeware main effect in the demo version, which does not apply a watermark.

Image Effects

Stereogram Lab Filter
... allows you to generate hidden image stereograms. These autostereograms consist of a repeating pattern and only show their hidden content if you focus your eyes behind the image plane.

FilterForge Freepacks
FilterForge will be offering so called Freepacks, which are are free Photoshop plugins based on the Filter Forge technology. Freepack 1 is a set of seven metal textures and effects. Freepack 2 contains seven photo effects, e.g. for adding sunny styles, grunge looks, color tints, age the image and more. Freepack 3 offers seven frame effects, e.g. a painted wooden frame or a vignette.The effects are fully adjustable and support seamless tiling.

Mezzoforce Plugins
Mezooforce offers a few Lite versions of its commercials plugins which are limited to processing only images up to 1000 x 1000 pixel in size. In order to download them, you need to subscribe to a discussion group. The Ice 2.0 Lite plugin creates ice-like structures. Version 1.03 of the same plugin is also offered for download and does not have any size limitation. Mezzoforce MetallEaser 2 LITE adds a metallic effect to images. The Snow plugin produces snow effects and has no size limitations.

Medhi Plugins
... contain 26 free Photoshop-compatible plugins that were created with Filter Meister. The plugin effects range from color effects, photo correction, transparency manipulation, distortion to grain and fractals. Version 2 of the Seamless Border plugin and the Flat Median plugin just became available. Additionally all Mehdi plugins were updated for Windows Vista compatibility.

Xero Plugins & Xero XL Plugins
... consist of 4 collections of up to 9 freeware plugins plus a new XL collection of five plugins. The effect range varies from color effects, art effects, grain effects to noise removal and image enhancement. It is a bit hard to get used to the pink dialog of these plugins, but otherwise they look quite useful. There are also five extra plugins for star, paint, snowflake, sparkle and tinted monochrome effects.

Martin Koch Plugins  
... contain three freeware plugins that produce line art and dithering effects. The Line plugin applies a 1-bit black and white horizontal or vertical line screen, Random Dither randomly dithers an image to 1-bit black and white line art and the Dither plugin uses a special dither effect that looks better than standard dithering algorithms. Finally, there is a fourth plugin that costs $10 and deletes stray dots in a line art image. The plugins only work on 8bit images.

Flaming Pear Freebies  
... consists of dozens of plugins. The Rule 30 plugin produces an abstract gray pattern, Veins transforms the image into color lines that look like blood veins, the three "Gray from" plugins produce B/W images and Pixel Trash tries to imitate the computer graphics of the early 80s. The Circle to Square plugin transforms circular objects in an image into squares. The Zombie plugin gives your images a touch of horror. It works best with portraits that show eyes and teeth. Most plugins apply the effect without showing a dialog except a few plugins.

Thedigitalartshop.com Plugins
Among various commercial plugins Thedigitalartshop.com also offers three free plugins. GREYSCALER is a kind of channel mixer for converting images to black and white. It also offers brightness and contrast sliders. IMAGE ENCODER encrypts and decrypts your images with a 24 bit key. IRIDESCENT applies a color-shift effect to your images.

AmphiSoft Filters & Photo Tinter
The Photo Tinter plugin allows extracting tone maps from existing black and white images and applying them to new images and is meant as an alternative to Photoshop's Curves filter. The AmphiSoft Filters contains both free and shareware Photoshop-compatible plugins. Included are free light versions of "Convolution shaman" and "Sorting shaman" (basic functions like blur, sharpen, edge detection and sharpening and despeckle with many extra options for image enhancement) which can be upgraded to full versions by registering. "Thread master" (cross-shaped smudge effect) and "Out of the noise (noise & diffuse effects) are free, too. The new and free Simplifier filter provides a wide range of color\shape simplification operations, resulting in "painterly" artistic effects. The shareware plugins of this package are called "Metalwork II" (metallic effects), "ArtiFactor" and "Kinetics lab" (for creating organic textures by simulating chemical reactions).

Photoshop-Scripts.com Filters - English web pages not available anymore
... offers several effect plugins, which are basically freeware and only available in Spanish language.To get access to them you need to contact the author, whose English is probably not the best. The plugins are called Watercolor, B&W, drawing, Dream, Threshold, Tone Effect, Splash, High-Key, Dynamic Color, Convolution Draw, Graduated Filter and Center Spot.

Mosaic & Illumination Fix Toolkit
... apply mosaic effects to images and let you fix unevenly lit photos.

L&K Filters
The free L&K Filters consist of 14 plugins that produce various gradients and patterns, which can be useful for graphical designs.

Richard Rosenman Filters
... include many freeware plugins. 3D Sphere Generator generates a 3D sphere, Color Bar Generator creates calibration bars, Scanlines creates simulate a monitor, Grid Generator creates custom b/w grids and Grain Generator produces varying types of grain on your image. Tiler makes an image tileable, Pixelate applies a pixel effect, Halftone creates dot patterns, Diffuse produces noise diffusion effects, Lens Distortion Corrector performs lens corrections, Spherical Map Correctorproduces texture map correction for spherical texture mapping and Diffuse Glow creates what its name suggests. Pinch adds a pinch effect, the Squarify plugin produces squared distortions and Evaluate can perform more than 50 image processing operations. The Portable PixMap Importer/Exporter filter imports and exports PPM, PGM and PBM images in binary and text format. The Superformula plugin draws a wide variety of geometric shapes, Smart De-Interlacer performs various de-interlacing procedures, Vignette Corrector removes vignettes, Pinocchio is a fun tool lets you prolong the nose of people and Color Replacer performs selective color replacements. Pixel Quantification filter calculates the sum of a selected number of pixels above a level threshold.

Little Ink Pot Free Plugins
... offers some free plugins). Xpose is a simple exposure adjustment plugin. Thredgeholder provides an edge detection algorithm that turns photos into line drawings. Chalkaholic Lite is a pluginfor drawing-style effects. There is also a Pro Version which offer more possibilities.

Econym Plugins - Currently Down
... are a free collection of 11 plugins for Photoshop and compatible applications. Effects include page curls, page rolls, color posterization, color tinting and some other effects. There is also a contrast masking plugin, which renders very slowly, and two plugins for correcting the brightness and contrast of 16bit images. The plugin dialogs are a bit small and maybe a bit too colorful. Nevertheless you may find the one or other useful plugin among them.

Cybia's Works Plugins  
... are 8 plugins with simple transparency, color, edge, emboss, grain and mesh effects. The old Windows plugins of each Works series have been combined to a single plugin, which lets you select the individual filters from a drop-down menu.

Namesuppressed Design
... offers a few Photoshop-compatible plugins with simple but useful effects. The AUTOINTERLACE plugin is freeware and creates the interlace effect as seen on television screens. AUTOCHROMATIC and SOFTENER (Win only) are full-functional shareware plugins that cost only a few dollares registration fee each. Autochromatic colorizes an image with two user-definable colors and Softener adds soft, glossy effects to your images. PLAID LITE is also a inexpensive shareware plugin for creating seamless plaids and tiling tartan patterns. It extracts colors and patterns from any digital image to create a color coordinated plaid pattern. The Plaid Lite demo version is fully functional, but displays several nag screens.

GraphicXtras Gothic Plugin
... adds a dark gloomy Goth effect. Unfortunatelly it doesn't show the correct result at the default preview zoom and doesn't display a progress bar during final rendering.

Luce
... is a plugins for creating light beams known as volumetric light.

 

DC Filters
Improved versions of 14 of the DC Filters (for Windows) are now available. The old FilterFactory versions were recompiled with FilterMeister which made several new features possible. These 14 plugins include some nice pattern, edge and distortion effects.

 

Ulead Free Plugins
Ulead started offering their commercial Art Texture plugin for free some time ago. Now they also offer Particle.Plugin and the FantasyWarp plugin (for Windows) for free, too. Particle.Plugin creates eight natural particle effects, e.g. smoke, fire, bubbles, clouds and rain. FantasyWarp takes any image or selection and warps, distorts and twists it into surreal patterns. Don't miss these plugins!

EyeCandy4000 BevelBoss & MotionTrial and Splat! Edges 
The Macromedia Fireworks MX trial version contains full versions of the BevelBoss and MotionTrial plugins of Alienskin EyeCandy 4000 and the Edges plugin of Alienskin Splat!. If you are lucky you may find the Fireworks MX trial an old magazine cover CD or somewhere for download on the web. After you installed it switch to the Fireworks folder and open the Plug-ins sub folder. Now copy the Splat 8bf and dll files, the EyeCandy 8bf file and the two sub folders to your default plugin folder. Open the image application you usually use to apply plugins and there they are!

Almathera Plugins
1997 Almathera developed eight Photoshop-compatible plugins. Unfortunately Almathera was closed down in the same year. Currently these plugins remain copyright but can be distributed freely in a non-commercial manner. This means that they can be used for commercial design work, but it is not allowed to sell the software itself. The Almathera plugins produce shape, bevel, halo, drop shadow, grayscale, warp, lightning and puddle effects. Although the interface is outdated and displays wrongly with "Large Fonts", you will certainly find one or two interesting effects in this package.

AutoFX Mosaic  
... released a second freeware plugin and standalone application called Mosaic. Mosaic makes your photos look as if they were created out of a mosaic tile. Photo-realistic depth, variable tile size and color options give this effect an infinite number of looks. Included with Mosaic are effect presets, a PDF manual and technical/customer support. The plugin requires a serial number which can be requested for free from AutoFX.

AutoFX Dreamy Photo  
... is a free Photoshop-compatible plugin and standalone tool from AutoFX that adds a soft-focus effect to photos. The effect is configurable with seven controls and by using presets. The interface looks like that of AutoFX's commercial DreamSuite product. The package also includes a PDF manual and promises technical and customer support. Dreamy Photo requires a serial number which can be obtained by submitting your e-mail address from a web form.

Filter Meister
... is a sophisticated filter plugin development tool. Beside the filter development plugin itself there are some interesting Photoshop-compatible plugins included that were created with Filter Meister. There is also a large library of source codes which can even be used with the unregistered version of Filter Meister and applied to the image. Among the code are e.g. Adjust Saturation, AFH Beveler 3.0, Patches Factory (animated), Box Blur, Nirvana, Fractalism and many other examples. Filter Meister is free to use, but if you want to compile your own plugins, you have to register it.

DragonFly's Plugins
"Sinedot Shader" creates shaded 3D sinus curves, "Shear" does a simple shear effect which means that you can specify a line along which the image is than shifted and "Retrodots" places holes in a symmetrical pattern on an image. The new "Sinedots II" now includes enhanced antialias, color support, blend modes, more parameters for enhanced control, 16bit support and enhanced compatibility. Two import plugins for .ico and .cur files are available there, too.

VDL Adrenaline Plugins
The Adrenaline series consists of several free plugins and two commercial ones.The "Harmonix" plugin creates wave lines known from sound editing tools. With the "Camouflage" plugin you can generate all kinds of army-style and animal camouflage patterns. "NightVision" creates realistic night-goggle effects including enhancement, anti-aliased interlacing, signal noise and feedback. "Snowscape" lets you add a snow effect to a layer. "Snowflakes" adds snowflakes of any size and shape to your images.

The Yellownail Collection
consists of 32 Photoshop plugins with the names: 13area, 1stImpact, 3DTile, Adjuster, Alchemist Pro, Ancient Paintings, BambooCraft, Bedlam, Bokassher, ButColor, ButtonMagic, ClassicalGold, CoolColor, CrazyTile, CuteMozaic, CycloidDistortion, DeftMove, DemonishCell, DemonishSkin, Eloquency, Embossher, Enhancer, EqualLevel, FillHarmony, FireWork, FlowerFrame, FlushIt, FoolishStripe, Gingum. These plugins were created by a Japanese programmer and offer some interesting effects you shouldn't miss. Some of them apply directly to the image while other have a Japanese dialog.
Unfortunately getting these plugins can be a bit time consuming and exhausting, because you have to download them individually and make your way from the main web page to a description page and from there to the download page. You have to do that for each of the 32 plugins and everything is in Japanese language.

 

Pobelly's Plugins - Currently Down
contain four free Photoshop-compatible plugins that still look a bit experimental. The "Eliminate Whatever" plugin will change opacity based on color or brightness. "Whack and Blight" converts color images to monotone or duotone while weighting of the RGB values. "Meet the Neighbors" is a 7x7 convolution plugin for playing with different operators. Finally, "Throbber Thinger" is though to make those little animations in the corner of browser windows, therefore doing some basic rotate, copy and fade operations to individual frames of an animation.

2D HyperClouds
... is a filter plugin for generating cloud textures and plasmas. It is based on Perlin's noise functions and uses the background and foreground colors to make the clouds palette.

 

Mura's Filters
Pole Transform transforms an image to polar coordinates or rectangular coordinates. You might know this effect from Photoshop. Cloud produces a seamless cloud effect, Copies blends multiple copies of an image and Seamless makes an image seamless by wrapping the edges around. (Orignal website http://mura.hey.to/ does not work anymore.)

 

Mark's Page Curl & Remove White
A plugin that creates a page curl effect and a plugin with a transparency effect.

 

Primus  
... is a free feature limited version of Blade Pro. You can use it to create nice text effects or beveled and textured shapes. It offers 16 presets and a slider for adjusting the bevel height. Unfortunatelly you can't use other than the 16 textures. You need to register it (for free) before you can apply the effects.

Axion Lens Flare32 and Glow32  - Currently Down
are two plugins for Photoshop-compatible applications and trueSpace 2.

AlienSkin Xenofex 1.0   - Not available for download anymore
2 of the 16 plugins (Crumple & Stain) work in the demo version.

Fantastic Machines Tile Tools
You can get 7 of these 21 plugins for creating tileable images and textures for free.

Filter Formula Example Filters
... are some filters created with Filter Formula.

Photo Enhancement

4N6site Plugins
4N6site.com offers four freeware plugins (for Windows), which are mainly meant for forensic tasks. "Color Deconvolve" separates or removes color components from the image, the Digitization plugin saves coordinates of features in large images a text file and the Fourier Transform plugin filters images in the frequency domain, e.g. for separating or enhancing periodical patterns. The "Warping" plugin lets you change the perspective of photos. It maps the image area that is enclosed by 4 definable control points to the whole image.

FoksMarx recolorLE
... is a feature-reduced free version of the commercial recolorST plugin. It can be used for color equalization, color enhancement, removal of color stains and bleaches and also for artistic color effects.

Pog's Plugins
... consist of five Photoshop plugins on his web site. Pog?s Lab Overlayer plugin performs blending in overlay mode, Variable Blurrinator applies a selective blur effect based on a brightness mask, the Mono Renditionizer plugin is a channel mixer with a few specialties and Lab Blender blends the image with itself in Lab mode. Pog?s Color Filtrator is a selective desaturation tool that offers specific hue ranges for creating B&W images.

8bf Plugin Filters
Jim Clatfelter's 8bf plugin collection was stuffed into two plugins: The AAA OPTIONS plugin offers more than 50 filter options and 16 blend modes and the AAA BLUR OPTIONS is a plugin that contains various blur effects. Nevertheless the old plugins are still available for download. The 8bf plugins are now also compatible with Vista.

 

Rudolf's Black and White Works 
... is a free filter plugin for converting color images to B&W. The conversion is done with the help of a hue and saturation slider. There is also an option for toning the images and a preset feature

Aphtophoto  
The Aphtophoto collection consists of three free plugins. The Exposure plugin simulates photographic exposure and lets you change the contrast. The Fix Focus filter is for rescuing oversharpened images by smoothing the edges. Finally, the Auto White Balance plugin tries to color correct an image without any user input.

Vicanek Plugins
Mr. Vicanek offers several free plugins. The Color Cube plugin provides a 3D visualization of all colors in an image, which can e.g. help to detect color clipping. You can spin the color cube and view it from any angle you want. The PanoWarp plugin performs transformations that are necessary for stitching panorama images. The Perspective plugin lets you pan, tilt, rotate, reposition and resize an image. The Pinocchio plugin is meant as a fun tool for distorting images and the Vignette Corrector removes or applies vignetting effects. The Contrast Mask plugin enhances images with too much contrast and also suppresses halos. The Sliding Tile Puzzle plugin lets you play this well known game. Unfortunately you can not apply the effect to the image.

Wire Pilot
... is a free plugin and application for retouching wires, posts, antennas and other unwanted linear objects from a photo.

Magic Enhancer Lite & Outliner
Image Skill offers two free plugins (for Windows). Magic Enhancer Lite is a plugin for brightening shadows, darkening shadows and adjusting local contrast as well as the color temperature. There is also a commercial Pro version with a few more features. The Outliner plugin turns your image into a line drawing.

Easyfilter Plugins
Easyfilter offers three plugins (for Windows) for image adjustment and color space conversion. The Image Adjustment plugin contains sliders for hue, saturation, lightness and contrast, and works in 8 and 16 bit RGB mode. The Color Space plugin converts from and to RGB, CMY, CMYK, HSB, HSL, Lab and LCH. The Color Converter plugin is quite similar, but also offers 17 different RGB working spaces for input and output. For the first two plugins you can also download the FilterMeister source code and inspect the algorithms.

SmartCurve
... from EasyFilter was developed for Photoshop Elements as a compensation for the missing Curves command, but you can use it in Photoshop and other applications, too. It supports RGB and Grayscale images with 8 and 16 bit color depth, displays a histogram and an Auto correction button.

 

Hotpixel, Bleach Bypass & Beautifier
HotPixel is a plugin for removing hot pixel noise from digital images. Hot pixels often occur when on long exposure photos. This plugin automatically detects and removes hot pixels without degrading the image. BleachBypass simulates the traditional bleach-bypass technique, which creates desaturated, grainy and overexposed results. A commercial Pro version of this plugin is also available. Beautifiercreates soft-focus, high-key and infra-red effects. It is meant for portrait and landscapes photos.

Fotomatic Plugins & Final Impact Vivida  
Cybia released eight free Fotomatic plugins and the free Vivida plugin from the otherwise commercial Final Impact series. Vivida is meant for adding impact to underexposed and dull photos by boosting the brightness, contrast and saturation in individual color channels. NightScope from Fotomatic is a filter for adding a basic "night-vision" effect to your digital photographs, Pseudo-IR creates a similar look as traditional B&W infra-red film and BW-Plus quickly turns your colour images into grayscale, but with the added option of using a colored optical lens filter. Hi-Spot creates high-contrast B&W effects as well as monochrome tints, G-Force is for B&W grain effects and Techni-X produces high contrast effects by bleaching out the midtones. SkyGrad is for tinting the sky area of photos. It overlays an increasingly transparent, colored gradient from top to bottom. The FastFix plugin corrects with the help of the brightness, contrast, saturation, and three color parameters. It is also capable of opening and saving presets.

Topaz DeJPEG
... is a freeware plugin for removing JPEG blockiness, fringes and other compression artifacts in JPEG images while maintaining image details and clarity.

True-Pro-Converter - Not available anymore
... offers a few B&W and sepia variations. It is commercial, but the demo version lets you apply its effects to 8 bit images. For using it on 16bit images, you need to buy the full version.

Simpel Filters
RGB Channel Mixer and Gray Scale Mixer are enhanced versions of the Channel Mixer in Photoshop and finally Color Space Converter lets you convert an image between various color spaces. There are also commercial Pro version of the two Mixer plugins available.

Photo-Plugins
George Fournaris offers five filter plugins (for Windows) called B/W Conversion, Local Contrast Enhancement, Soft Focus, Contrast Mask, Gradient Blur, Lens Corrector, High Pass Sharpening and Selective Saturation for free. Additionally the ppLabCor plugin corrects a bug in the current version of ColorLab* that concerning Lab TIFFs.The most interesting one is probably the B/W Conversion plugin which offers a lot of options for creating B/W images. The author asks for a donation via Paypal if you like and use his plugins.

Gradient Remover & Vignetting Remover - Not available anymore
... from Rob Miller can be used with 8bit and 16bit RGB images for removing vignetting and background gradients from astronomical photos. Normal photos work, too. It is freeware, but the author asks you to donate $5 if you like it.

DOP Plugins
Outback Photo offers two automation plugins for Photoshop called DOP Tonality Mask and DOP Upsizing. DOP Tonality Mask creates seven selection masks for shadows, midtones and highlights and is limited to images up to 2000x1500 pixel. For larger images you need to buy the commercial version. DOP Upsizing is freeware and implements a special upsizing technique. Both plugins only work in Photoshop CS and CS2.

Multiple Exposure & BW Conversion
Rob Williams offers two plugins that are fully-functional shareware. The Multiple Exposure plugin creates abstract multiple exposure images from a single photo and the BW Conversion plugin converts images to B/W with the help of a few color filters. If you intend to use these plugins, please contribute $20 to Mr. Williams for his efforts, otherwise he may decide to make his plugins fully commercial.

Fiddaman Plugins
Tom Fiddaman offers six free photo correction plugins (for Windows) that were created with Filter Meister. The SelfToner plugin tones images from their own palette or with tones from other images, PFree reduces purple fringing whereas CAfree reduces blue fringing and NoisePlot visualizes noise. Finally, the Luminosity plugin is meant for highlight and shadow correction and Reluminate performs luminosity adjustments. The plugins aren't that easy to use, because many sliders have very technical names and only a few explanations are offered on the product pages. Additionally many slider settings produce effects that aren't that desirable, so you need to fiddle a lot with the sliders. Nevertheless it is worth trying them.

virtualPhotographer
... allows you to create a variety of photographic styles. Effects like film grain, soft focus, B/W, B/W tinting and high contrast can be applied to the image in one step. It also offers many presets which can be fine tuned for your requirements.

Reindeergraphics.com Plugins  
... include several free plugins for photo editing. The Wide Histogram plugin displays enhanced histogram of 16-bit images. The plugin provides a 512, 768, or 1024 pixel wide histograms and eight modes for the histogram, including RGB, Red, Green, Blue, Colors, Hue, Saturation and Luminance. The Custom Filteris an enhanced version of the custom/user filters that can be found in various image applications. It supports a 7x7 convolution array, accepts real (floating point) numbers for greater precision and lets you save and open presets. The Adaptive Equalization plugin increases the local contrast of images by reducing overall dynamic range. The Enter Magnificationfilter calculates the length of a calibration bar. TabbedText reads and writes a grayscale images from and to a tab-delimited text file. The text file can be created and manipulated in a spreadsheet like Excel or produced with text output from any arbitrary source. The Select Edges plugin creates a selection from the contours of the edges in the image. With the help of that selection you can selectively process the image with other filters like Gaussian Blur or Unsharp Mask.

ChannelMixer - Currently Down
... is a freeware plugin that is meant for Photoshop Elements users, which don't have a tool with that name in their application. Unlike Photoshop's ChannelMixer it lets you only do custom conversion to B&W and no color effects. Unfortunately this plugin has the same problem as his Photoshop counterpart: it doesn't keep brightness constant when converting to B&W, so you have to be careful when using it.

Flo's UnDistort filter
.... is a plugin for correcting deformations of photographic images, e.g. barrel and pincushion deformations, perspective deformations and chromatic aberrations. The demo version is completely functional for images smaller than about 800*600 pixels. For processing bigger images, you have to purchase the full version for $15.

Polaroid Dust & Scratch Removal Utility   
The Polaroid Dust & Scratch Removal Utility consists of a standalone application and a plugin. The application offers various tools for creating selections whereas the plugin offers an interactive preview which makes it easier to create the desired effect. Although it sometimes renders quite slowly, it is a nice addition to the Dust & Scratch Removal tool in some graphics applications.

Sharpen filter
.... is a very simple filter which lets you only adjust the sharpness intensity. It is a bit superior to the Sharpen filter that is built into many image editing applications. The download link for this filter is at the bottom of the page.

Colleen's Photoshop Fun Pack
5 filter plug-ins for Adobe Photoshop for Macintosh. Rotate Color rotates the color in the RGB space. Create B/W creates black and white (gray scale) images from color images. Kwick Mask creates a selection from RGB images. Adjust Saturation gives you more control over the saturation adjustment. Modulate Color modulates the HSB value of the image using the mask value. Variable Blur achieves soft-focus effects very easily.

AIM DeepSpace & Photoshop Plugins
Some plugins with basic image manipulation functions plus 5 other plugins: The GAMMA filter applies the accurate gamma transfer function, DENSITY provides density conversion which can be useful in creating a density mask. SPACE HUNTER is useful as the first step in editing images of unknown working space and generally for hue, saturation and white-balance corrections. USM is a Unsharp Mask filter.

Metrix
... is a plugin for adapting two images to each by match the colors of both images. The adapted images can e.g. be used to create a panorama image. Only works fine with very similiar images.

Red Prince Flips 'n Rolls, Noise Generator, Whitewash & Pixie Dust
Flips 'n' Rolls is a collection of 19 plugins without dialogs that flip, roll, invert and reverse the order of bits in the RGB channels. The Noise Generator plugin creates a noise effect and the Whitewash plugin makes white colors transparent. The Pixie Dust collection consists of 19 plugins (only some of them have a dialog) that create various simple contrast, brightness, monochrome and solarisation effects.

Web Design

3D Shadow
Lokas Software offers the free 3D Shadow Photoshop-compatible plugin. It creates various types of 3D shadows from a selection. Settings include transparency level, perspective, shadow color, position and X/Y/Z angles. The preview only shows the image at 100% and there is no zoom option. This makes it very hard to adjust the effect if the selection is almost as large or larger as the preview.

WebClipper & PhotoHTML
"WebClipper" from Boxtopsoft corrects the color drift from Web safe colors that often happens during color reduction and allows you to create hybrid images combining custom and Web safe colors easily. Hybrid images allow for greater image quality than those color reduced to the Web safe palette, while still largely eliminating most unwanted dithering when images are viewed on 8-bit Windows systems. "PhotoHTML" converts any image to an HTML table. Each pixel in the image becomes a 1 x 1 pixel colored cell in the table.
 

Gregory Paret's Plugins  
"Grids" is a plugin for placing grids on your image, "Polygons" draws N-sided polygons and a circle, "Color Counter" counts the colors used in an image, "Selection Outliner and Un-Featherer" finds the rectangular outline of a selection and has options to remove feathering from a selection, while the "Gamma Filter" tries to compensate the fact that the Photoshop Levels control does not do an arithmetically consistent Gamma adjustment. Finally "HTML Color Tags" which is only available for Windows displays the current foreground and background in hexadecimal format.

NRV Bordermania Pro
The Bordermania filters are designed to create a variety of basic borders and buttons around images and are suited for creating buttons for Web pages. BorderMania Pro is free for a 30 day evaluation period and after that a license fee of $10 is required to use the enhanced features. If you don't register them, the filters continue to work, but lack special Pro features.

Extensis PhotoBevel  
... instantly creates inner and outer bevels on any part of your image or text. Lets you adjust bevel width, softness, highlight/shadow balance, intensity, and light direction.

Extensis PhotoText  
... applies bold, italic, outline and shadow styles without requiring the corresponding printer fonts.

Patterns / Textures

 

Background Maniac Filters
Various plugins that produce knitted backgrounds, oriental patterns and other cloth textures. There is also a tutorial that shows how to create plaid patterns with one of the plugins.

Redfield Freeware Plugins
Jama 3D and Lattice Composer are two 8bf plugins for creating cellular and mesh structures from 2D images, as well as 3D shapes and backgrounds.
Seamless Workshop creates seamless tiles of any image by cross blending the borders of the image. Water Ripples creates realistic water ripples and produces unlimited variations of rippled surfaces. The Craquelure 3D plugin creates a wide range of well known craquelure effects.The Face Control plugin allows you to change facial expressions in a simple fashion. Human, animal, alien, or any other kind of faces are possible. The Redfield++ Bas-Relief filter plugin turns 8-bit RGB images into a carved-in bas-relief with controlable surface lighting. The effect can also make the image look like aluminum foil, hammered metal, carved stone or pencil sketch.

Birgits Chaos   - Currently Down
... is a set of 19 plugins (for Windows) that produce nice fabric patterns. They were created with FilterMeister.

Tessela Plugins  
Eric Jones also offers two nice plugins (for Windows) called Tessela and Check Out. They generate nice kaleidoscopic and chess-like patterns.

Filter Farm
is a freeware plugin that creates colorful noise effects according to random algorithms.

Painting & Drawing

Deep Paint 2
Right Hemisphere decided to discontinue their DeepPaint 2 product and make it available for free. Deep Paint is a painting tool that offers artistic photo-cloning, fully editable brush and canvas settings. It simulates oil, acrylic and watercolor brushes. Deep Paint works as a Photoshop plugin as well as standalone application. For more information see here.

Fantastic Machines' Paint Engine
... has different presets for turning photos into paintings.

Wacom Pen Tools  
... for working with a Wacom tablet.