Two projects to submit fonts to, or find others to work with:

Typeforge
http://www.typeforge.net

The Typeforge project was initiated by Portuguese type designer Pedro Amado, to create a platform for “open source collaborative type design”. You are encouraged to share sketches, notes and ideas and work on collective projects. Good Fontforge tips + tricks too!

Open Font Library
http://openfontlibrary.org/

Based on the same principle as the Open Clip Art Library, this project simply aims to bring together copyleft fonts. The project has just started, hence their collection is rather small, but such a repository is so much needed that I think it could grow quickly once people start adding.