While studying Chinese, I heard about a program called Supermemo. It was apparently quite difficult to use, only ran on Windows, but also helped people learning things extremely well. Not just any flash card program, it would bring up cards automatically as you were about to forget them.
I decided I would buy it, but then I noticed a new version comes out roughly every two years, the last being Supermemo 2006. I did a web search for Supermemo 2008, and got an answer saying it probably would not come out until sometime in 2009.
Fair enough, but in related FAQs, they had some information about the lack of Supermemo for Mac OS X. That link has a list of alternatives that can be used on the Mac. Out of that list, I found Anki to be very promising (particularly for Japanese study) and Quizlet as an excellent source of flashcards, so I don’t need to input them myself by hand.
Lucky for me, Anki is free! It also will run on Linux or Windows should my preferred computing platform change again in the future.