There’s a lot of discussion doing the rounds at the moment about the quality of recorded music. It all starts with the source material and how well the people making the music know what to listen for.
Philips have create the cool website where you can take some test to see how well you detect changes in sound on the same piece of material. It isn’t perfect and it won’t get you a degree but it’s an excellent way to give your ears a spin.
Furthermore, if you want to help your friends who listen to MP3s hear how different things can sound then this may be a great way to introduce them to critical listening.