Anki

Anki is a program which makes remembering things easy. Because it is a lot more efficient than traditional study methods, you can either greatly decrease your time spent studying, or greatly increase the amount you learn. Anyone who needs to remember things in their daily life can benefit from Anki. Anki is content-agnostic and supports images, audio, videos, and scientific markup (via LaTeX).

Anki lets you study on your own computer, online, on your cell phone or other portable devices like an iPod touch. Synchronization features let you keep your information across multiple computers. Shared decks allow you to divide work between friends, and let teachers push material to many students at once. Anki runs an intelligent scheduler based on the SuperMemo SM2 algorithm. The flexible fact or card model allows you to generate multiple views of information, and input information in the format you wish--you are not limited to predefined styles. Anki is fully extensible, with a large number of plugins already available. Anki is open-source and optimized for speed--it will handle reviewing decks of 100,000+ cards with no problems.