iFlash

From Mac Guides

iFlash is a multi-sided flash-card application for Mac OS X. Users can choose to keep the original front/back orientation of typical real-world flash cards, or choose to add an unlimited number of additional sides to increase information instances on the same subject. The app allows for multiple "decks" of cards. Users are encouraged to use an existing online catalog of previously-made decks, as well as upload completed decks of their own.