I'm surprised there isn't one here for law. Enough people want to know specific legal areas (not enough to practice, just enough to understand the system), that I think this could be a very interesting area to make a codeacademy-like site for. For instance, I know a lot of people that would like to learn basic property/renting law and find it too difficult to go over all of the bylaws and learn whats what.

Edit: Also wanted to say, good list!