SVK is a decentralized version control system written in Perl which uses the Subversion filesystem.
SVK takes Subversion as it's base and adds these features:
The main think that SVK brings to the version control party is disconnected development. You disconnect from the central server by making your own mirrored copy of that repository. This means that you can do all your version control without requiring a connection to the main server. Once you have reconnected to the central server you can merge your changes into the central copy, or you can make your changes available to others so that they can merge your changes into theirs.