Here is a list of plugins for After Effects courtesy of Steven Gotz, who also has a bunch of links about other platforms such as Adobe Encore or Audition.
|Free After Effects plugin for making animated flame fractals.
|Filters and plug-ins for Photoshop and After Effects
|Aspect Ratio Converter
|Premier filter plugin, which converts anamorphic 16:9 to 4:3 letterbox, and another that crops standard 4:3 to letterbox.
|Burger’s Transition Site
|Free transitions for Adobe Premiere, Ulead Video Studio, Ulead GIF Animator and Ulead MediaStudio Pro.
|Plug-ins for After Effects, Premiere Pro and FCP
|Collection of plugins with Free trial, and two free plugins for AE and FCP
|Free After Effects Plug-in. A simple utility that copies the current composition image to the Windows Clipboard, allowing easy pasting into other image applications (such as Photoshop). It bypasses the task of saving the current frame to an image file and then reopening.
|Plugins for slow motion and much, much more
|Pete Warden’s Video Effects
|An interesting collection of free After Effects plugins. Try them out.
|One-stop source for all of your favorite plug-ins
|Digital Tools for Digital Artists
|The Pure Motion Noise Reduction Plugin is a perfect tool for the video user who wishes to produce movies of the highest technical quality. Available for Editstudio 5, Adobe Premiere Pro and Premiere Elements
|The Plugin Site
|Your guide to image and video effects
|Twixtor enables you to speed up, slow down or frame rate convert your image sequences with visually stunning results