Darcs

Darcs is simple yet advanced revision control system. High points:

• amazingly simple for a system so powerful
• written in Haskell
• based upon a "Theory of Patches" that enables it to do some cool things (such as cherry-pick)
• offers easy distributed development model (HTTP, ssh, emailed patches)
• change sets (as patches)

Low points:

• some corner cases are handled poorly (such as taking a very long time)

Home page: http://www.darcs.net/