One of many free distributed version-control systems

while the various DVCS systems all have differences, they all have more in common with each
other then they do with any of the non-distributed ones.

and just like learning CVS gives you a head start if you then start using Perforce, learning
any one DVCS system will give you a head start in understanding the rest of them.

there's value in entering this new area, even if the particular tool that you start with
doesn't end up being the one that you keep useing.