A Flashcards tool

jMemorize – Learning made easy (and fun) – A Leitner flashcards tool:

jMemorize is a Java application that manages your flashcards by the famous Leitner system and makes memorizing facts not only more efficient but also more fun. It manages your whole learning progress and features categories, statistics and a visually appealing and intuitive interface.

Looks useful. Also looks like something fun to build as a web service or Flash application.