CVS is good, but has a bit of a learning curve to it (it's true home is in the Posix world, so it's designed primarily to have a command line interface). Perhaps someone can recommend a good GUI front end to it.
Vault is good as well if you're used to something a bit more like source safe. (However, note that the Vault server software isn't free)
Vault is good as well if you're used to something a bit more like source safe. (However, note that the Vault server software isn't free)