AnkhSVN open source (free) Subversion SourceControl Provider.
AnkhSVN - Subversion Support for Visual Studio
The 100% Opensource Source Code Management Solution for Microsoft Visual Studio.
AnkhSVN is a Subversion SourceControl Provider for Visual Studio. The software allows you to perform the most common version control operations directly from inside the Microsoft Visual Studio IDE. With AnkhSVN you no longer need to leave your IDE to perform tasks like viewing the status of your source code, updating your Subversion working copy and committing changes. You can even browse your repository and you can plug-in your favorite diff tool.
AnkhSVN is an active open source project with multiple committers from around the world (including CollabNet). AnkhSVN is currently in release 2.6. For a list of features and bugfixes in this revision, check out the change log.