GALEN WILEY  iFlash is simply a god-send for students in all grades and subjects. Its practical, free-form design make the possibilities almost endless, and making a virtual card deck has never been easier (Literally, a card can be created in about two clicks, disregarding the typing).

The interface was incredibly intuitive, just as any self-respecting Mac OS X app should be, and the best part? It's free. (As always, donations are appreciated.)

It is indisputably the best flash card software I've used to date (and believe me, as a sophomore in high school with at least one vocabulary test a week, I've used a lot). I would highly recommend it to any and all students out there hoping to raise their grades. It has served me quite well, and it beats the heck out of carrying a stack of index cards around!  
(Version 1.2.3)