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).

More information can be found on the darcs homepage and on the darcs wiki.

Also feel free to check out the projects in the repository and send patches.