Adobe also offers free the Software Development Kit for Photoshop 5 plugins, which includes documentation in PDF format and sample code, with a couple of sample filters, the only usable one being the Shape filter.

They have released Force BW, a little plugin to help you get pure white or pure black when indexing colors in PS.

Finally, their PhotoDeluxe software includes two no-settings filters : Page Curl and Remove Red Eyes ; and also an import plugin for .wmf vector files.