Git_immersion is a project mainly written in Ruby, it's free.
Git Immersion Training (initially given at RailsConf 2010)
h1. Git Immersion Labs
p. These are the labs for the Git Immersion training, a series of self-paced exercises that take you through the basics of using git.
h2. Online
p. You can find the labs online at "http://edgecase.github.com/git_immersion":http://edgecase.github.com/git_immersion.