SVNSVN (Subvsersion) is a great Source Code Management tool - and it's free. Below are some links to help you get started.
VisualSVN Server - Freeware - extremely easy Windows setup of SVN Server.
Official Command Line Client - Freeware - you dont HAVE to have it, but you should. This client is needed for things like build automation scripts, etc.
TortoiseSVN Client - Freeware - the best way for working with SVN in Windows.
VisualSVN Client for Visual Studio Integration - Commercial Software - If you insist on Visual Studio integration, this is one way to get it.
AnkhSVN Client for Visual Studio Integration - Freeware - Alternative to VisualSVN Client.
RapidSVN - Freeware - Alternative GUI for SVN management.
Free E-Book on Subversion
Rick Strahl's guide to using SVN.