TortoiseSVN - The coolest interface to (Sub)version control
kdeSVN - Comfortable graphical SVN client for linux.
VisualSVN - VisualSVN - Subversion plugin for Visual Studio
SmartSVN - SmartSVN is a graphical client for the Open Source version control system Subversion (SVN).
SnailSVN - Similar to Tortoise SVN for Windows but integrated into Finder
Xversion - Super easy enterprise class version control.