Wikipedia / Concurrent Versions Systemoperates as a front end to Revision Control System (RCS), an older version control system that manages individual files but not whole projects.
Apache SubversionEnterprise-class centralized version control for the masses
Apache SubversionIts goal is to be a mostly compatible successor to the widely used CVS.
Mercurial SCMis a free, distributed source control management tool.
Wikipedia / Mercurialis a distributed revision control tool for software developers.
Darcsis a free and open source, cross-platform version control system, like git, mercurial or svn but with a very different approach: focus on changes rather than snapshots.