Most plugins below are usable with all versions of Photoshop under Mac OS X, 9 and earlier, and Windows (if you need a version that's not here, please write to us). Should also work with Elements, AfterEffects, Premiere, PhotoDeluxe, Corel PhotoPaint, Paint Shop Pro, Fireworks, Painter, Photo Impact etc. (incomplete list). For information about using these and other Photoshop plugins with the Gimp (on Linux), see this page and issue 6 of fullcircle magazine.
An easy way to create your web site's favourites/shortcut/bookmark icon in Photoshop. FREE, $5 donation suggested if you love the plugin. (MacHouse has a video tutorial on making a favicon.)
(If you're looking for a plugin for OS X 'icns' icons, try Zonic IconLab.)
This plugin lets you grab image layers from any PSD/PSB file. It's faster than opening the whole PSD in Photoshop, if you just want a layer. Also, it lets you open PSD created by the newest versions of Photoshop, in older Photoshop versions that cannot read them directly. Most importantly, it can usually recover image layers from corrupted PSD files that Photoshop won't open (if Photoshop opens with damage, this plugin recovers a more intact image).
FREE - small donation suggested if it saves your day/sanity/job.
A compatible and improved replacement for Adobe Filter Factory. Now fully scriptable!
FREE, $5 donation suggested More info.
Also see Filter Forge: seamless textures, visual effects, distortions, patterns, frames and more. Filter Forge has released 4 free plugins, comprising 7 filters each.
Improve throughput of your .img files for use in Electric Image Animation System in excess of 100X! If you work in EIAS Animator you cannot do without this one. A typical benchmark saving 57MB file:
FREE, $5 donation suggested.