Mnemosyne
Mnemosyne is a software package which supports a flashcard based method for memorization used spaced repetition. It allows you to create decks of flashcards containing information to be memorized, and then schedules them for you to review. The review schedule is automatically modified based on your performance on each item. Mnemosyne is open source, and is available for free for Linux, Windows, and Mac OS. Data collected by Mnemosyne can be contributed to the Mnemosyne project to help with research into memorization techniques.