The Mozilla Community, founded January 14 2005 by me at work, is intended to be the wiki for the Mozilla community. We host the Mozilla Materials project, the Standardized Letters project, and many other SFX projects.
Since the Mozilla Community is a wiki, any of its pages can easily be edited by anyone, at any time (there are some rare exceptions, where a page is protected from editing). The purpose of a wiki is that anyone can help build it — so feel free to chip in!
There is also a development-only Mozilla wiki, currently located at wiki.mozilla.org. They are more strict on content regulations and non-development related material is not allowed. There is also the Knowledge Base wiki.
You can download Mozilla Community's most recent database dump by clicking here.