If you do software development, you know how important source code configuration management is. Apple currently supports CVS, Subversion and Perforce in Xcode 3.x.
Over the past few years a new system called Git has been developed (by Linus Torvalds and other Linux developers) for use in distributed, non-linear development projects.
These days, a lot of iOS development projects are using multiple developers scattered all over, and a SCM system is absolutely necessary for there projects. We'd like to use Git, but Apple doesn't support it yet. Xcode 4 is supposed to.
If you're on a Mac, and if you do iOS development you are, you can find a good, free Git client called GitX. It has the following features, several of which are Mac-specific:
Mac OS X Hints
http://hints.macworld.com/article.php?story=2010121505123911