Open Circuits Wiki
This is pretty neat:
Open Circuits is a wiki for sharing open source electronics knowledge, schematics, board layouts, ports and parts libraries. This include open hardware Music Players, atomic microscopes, PC, PDA and mobile phones, and batteries. Please help us to build this resource by submitting your component descriptions, projects, techniques, and PCB footprints.
Basically, Open Circuits Wiki works very similarly to Wikipedia -- a web reference built around an open model in which anyone can contribute to the site and edit its contents. Only this site's focused on electronic circuits and knowledge.
How cool is that?