Flickr Anaglyphs Group - Insanely active Flickr group. Great place to post 3D photos and get feedback. Very supportive community.
Flickr Stereo Creations, Art, Manipulations and Games - From 2D-3D conversions to stereoscopic fractal art - it's all here.
Yahoo Anaglyphs Group - Great discussion, tutorials, tips and articles.
The Stereo 3D Channel on Vimeo - Excellent curation of high-quality stereoscopic videos. Experiments, short films, animation and more.
James Long 2D-3D Conversion - The master at 3D conversions. Don't miss his old family photo gallery. Incredible stuff.
Swell 3D - Self described as "a website full of things to look at with your 3-D glasses." I agree. Lots of fun. If you like 3D Manifesto you'll love Swell 3D.
Meant to Be Seen - Huge Stereo-3D resource. Excellent news and a very active forum.
3D Glossary - 3DGuy.tv's excellent glossary is a great place to get familiar with 3D concepts. Fairly technical, and very complete.
Wikipedia: Stereoscopy - History can be fun!
StereoPhoto Maker - Free software for editing stereo pairs. Get it. Learn it. Love it. (Windows only, but runs fine in emulation on Intel Macs).