On the Symfony project blog there's a recent post from <>Fabien Potencier about the popular framework's development and source moving to a new home - github.

As you might have noticed if you follow me on Twitter (which you should do as I make a lot of small announcements there), or if you monitor the Subversion activity closely, the Symfony 2 code is now hosted on Git. [...] So, from now on, all the development activity for Symfony 2 will take place on the new Git repository.

He briefly covers what git is and a resource (book) he used to help understand this recently popular version control system. If you don't want to learn a new version control system but still want to contribute back with the subversion knowledge you're already armed with, you can still use their svn mirror to get the latest releases.