I was invited to give a talk on Git to NSCoderNightLondon last week, and the slides have been made available as both a Keynote document and a PDF. The presentation was really an interactive one so there's not that much explanatory text; it may not stand up on its own that well. Still, if you're interested, you can see that. Thanks to @Abizern for organising.
For those that are interested in a little more explanation, you can see a similar screencast I made available for the Eclipse DemoCamp London this year about Eclipse's Git team provider.