Subversion is becoming a very popular choice for managing revisions of your files. It is very similar to CVS but it offers several improvements on top of it. Our development team just released the production version of the Subversion extension to JDeveloper which you can now get through the check for update features.
The extension offers all the basic features to help you manage your code in the repositry. One very nice feature is the visual resolution of conflicts. So if someone changed the file you are trying to commit and your changes ends up as conflicting - JDeveloper will give you a three way merge window that helps resolve these conflicts.
I've been playing around with the Subversion extension the last couple of days as part of the QA effort and I think that the next time I'll need a repository to keep track of a project - it will be Subversion instead of CVS.
To get you started using Subversion in a JDeveloper environment check out the new Subversion developer guide on OTN.