TortoiseSVN is a Subversion client, implemented as a windows shell extension. The coolest Interface to (Sub)Version Control.
Using TortoiseSVN Plugin for Eclipse 3.x you can acces to this incredible software inside Eclipse.
It is a really easy to use version control / source control client under a GPL license, i.e its free!
Since it's not an integration for a specific IDE you can use it with whatever development tool you like.
If you're not sure if TortoiseSVN is the best SCM solution for you, check out the SCM comparison.
Features of TortoiseSVN/Subversion
Windows Shell (Explorer) integration. Can be used without any IDE.
Icon overlays show immediately which files/folders need to be uploaded (committed) to the database.
Easy to use dialogs for version control operations
The UI is available in different languages.
Global revision numbers. You can get old versions of your project and not just single files.
Atomic transactions. Interrupted operations don't affect the repository at all.
