Git - Git is a free and open source version control system designed to handle everything from small to very large projects with speed and efficiency. It is easy to learn and lightweight with lighting fast performance that outclasses competitors.
TortoiseSVN - The coolest interface to (Sub)version control
Mercurial SCM - Mercurial is a free, distributed source control management tool.
SnailSVN - Similar to Tortoise SVN for Windows but integrated into Finder
Atlassian Bitbucket Server - Atlassian Bitbucket Server is a scalable collaborative Git solution.
Xversion - Super easy enterprise class version control.