Darcs is a distributed revision control system. It can be used to keep revision of documents (which includes sourcecode). I tried to use it to keep some projects. The repository is online at http://darcs.peterstuifzand.nl and is read-only.
The nice thing about darcs is that anyone can be
get a version of the repository on his
own computer. That repository is a complete repository and can be used to keep
revisions locally. Changes can be
push-ed to or
pull-ed from the remote repository. This
makes it easy to work on a local copy, while keeping different revisions (actually patches).
Also feel free to check out the projects in the repository and send patches.