Git is a free and open source
distributed version control system designed to handle everything from small to
very large projects with speed and efficiency.
Git is easy to learn and has a
tiny footprint with lightning fast performance.
It outclasses SCM tools like Subversion, CVS, Perforce, and ClearCase
with features like cheap local branching,
convenient staging areas, and
multiple workflows.
Pro Git
by Scott Chacon and Ben Straub is available to
read online for free.
Dead tree versions are available on Amazon.com.