I started using SourceTree a week ago to as a GUI to local Git repositories. I'm comfortable using Git from the command line, but I find a GUI helpful when looking at history or selecting which parts of the current working tree I want to commit.
It's currently free, but I would pay to use it.
Offers a good overview of core features, plus links to documentation and the Pro Git book to learn more about each topic.
I've been using this library for my own dotfiles for the last year. I packaged it up and released it today to see if others would find it useful.