Git is an open source version control system designed to handle very large projects with speed and efficiency, but just as well suited for small personal repositories; it is especially popular in the open source community, serving as a development platform for projects like the Linux Kernel, WINE or X.org.

It’s very “distributed friendly”.  Everyone is their own branch, basically.  Offline development is a cinch!  You can also be confident you are never going to mess up the trunk, if there was one.  The tutorial is short and worth taking a look, at http://git.or.cz.