TortoiseSVN (open source)

[Tami]

[url=\"http://tortoisesvn.net/\"]TortoiseSVN[/url] is an easy to use SCM / source control software for Microsoft Windows and maybe the best Subversion client there is. It is implemented as a Windows shell extension, which makes it integrate seamlessly into the Windows explorer. Since it's not an integration for a specific IDE you can use it with whatever development tools you like.

Another advantage of this shell integration is that not only web or software developers can use it but all the people who don't have the development tools installed, for example translators, doc writers, ...