Shlomi Fish has compiled a Comparison of SCM Systems (SCM is Source Code Management, or version control system). The list is pretty good, and had a few products I hadn’t heard of yet. Interestingly, the very feature I liked most about Darcs and Arch (their server-less topology) is missing from his comparison.
But Shlomi himself seems to be a bit of a oddball. See his $20 million needed for the “Better CVS” Initiative page, for example.