Aaron recently pointed me at Anki, an open-source flashcard system. I’m using it to refresh my Spanish language skills, but it’s a very generalized system that one can use to remember just about anything. You create linked “facts” (n-sided flash cards) and study them on your desktop, the web, or even a phone. It reduces the overhead in studying a lot, and there are thousands of “shared” decks of flashcards you can use or build on.