Mazes & Minotaurs reimagines Dungeons & Dragons with Greek mythology rather than Tolkienesque fantasy as its key inspiration. Free PDF downloads of rules, supplements, and adventures.
I used to play Scion which used lots of Greek mythology as well. It is set in modern day though. Pretty cool game, and it's all D6 based, which is an interesting change. Worth checking out if you're into that kind of thing.