Here's one thing that's been taking up a little of my time lately. It's a program from Harman Audio called How To Listen. It's used by Harman to train people on how to critically listen to recordings and evaluate their quality. I haven't been able to play around with it too much yet, but eventually I plan to take some time every day to complete some of the exercises.
So far, I've looked at the band ID module, and it starts out fairly easy, but as the number of bands increases it gets much more difficult. Around 5 bands, my scores started dropping pretty quickly.
To learn more about the program, you can head over to this link: How To Listen: A Course on How to Critically Evaluate the Quality of Recorded and Reproduced Sound.
To download the latest version of the program go here: How To Listen Version 2.04
Just as a side note, you'll need some fairly nice headphones for this to work well. Speakers probably won't be adequate.