Speed learning tool

I've started using supermemo.net to help me learn Ruby. You take notes in a question and answer format, then the software works out how often you should be asked each question based on how well you answer. I find that taking notes in a Q&A format is a good idea in itself because it exercises active recall rather than passive recognition. The repeat frequency calculations should take some of the drudgery out of memorisation by making the exercise more efficient.