Gregory's ServerIt doesn't help with the git model (or the myriad of oopsies like, "I rebased and can't push to remote anymore," and "I checked out a floating HEAD what is a floating HEAD oh god"), but at least it provides a UI layer that might help keep them from straying into that territory in the first week.
@trurl oh neat, I didn't realize Tortoise did a git implementation! I used their SVN integration for along time.
(Unfortunately, I'm now developing on three platforms for five, so I can't consistently use Tortoise.)