Seconding this. It's the most fun I've ever had on a technical project (with the possible exception of tptacek's microcorruption.com), and really opened my eyes to all the problems you have to solve to get a working computer.

Note: you can also complete all the course materials just by going to nand2tetris.org.

My presentation slides promoting nand2tetris to the Austin python group: https://docs.google.com/presentation/d/1fGf2eZVOM2lHL8hFVyd2...