Mac OS X only: Freeware flash card application Genius helps you memorize information by testing your knowledge using what it calls a “spaced repetition” method, which adjusts how often a card is repeated based on your performance over time. The application has a strong following, meaning you can download tons of user-submitted flash card sets covering everything from language to marine biology. Genius is freeware, Mac OS X only. If you plan on making your own flash cards for Genius, be sure you read about how to make effective flash cards first.
Genius