Cramberry: make studying easier with web-based flash cards
Cramberry supports multiple sets, and you can make them public, in case you've got study partners you want to share with. To make a card, just enter the text for the front and back. Sorry, art history students, but there's no image support yet. Once you've got your cards set up, Cramberry will quiz you. The best feature is that the cards you're getting wrong most often show up more frequently, to give you extra practice. Cramberry threw a few php errors during my test, but it works smoothly for the most part, and it's a great concept.