I really like this: http://jsoneditoronline.org/

Really cool man, nice work!

IMO the best way to learn and understand git is to use the command line. There are tons of places to visualize how it's working, like this: http://pcottle.github.io/learnGitBranching/ Plus, the command line forces you to do things step by step, which can help prevent unwanted commits and such.