TortoiseSVN - The coolest interface to (Sub)version control
Subversion Edge - What is Subversion Edge? A certified software stack containing the latest versions
SnailSVN - Similar to Tortoise SVN for Windows but integrated into Finder
uberSVN - Free, easy to implement UI for Subversion which includes:
RapidSVN - CollabNet, Facilitating Collaborative Software Development
Mercurial SCM - Mercurial is a free, distributed source control management tool.