And now for something completely different... a full implementation of a CHIP-8 interpreter, complete with "sound" (via the Web Audio API).
But why? Well, it all started when I fell over a link to an article about Another World, and ended many hours later with the complete (as I can be bothered making it) CHIMP-8 interpreter! Feel free to have a peek at the source on GitHub, then go off and implement your own. CHIP-8 is the perfect interpreter/VM to get your feet wet with.