While iTunes' "Genius" function is friggin awesome in that it puts together songs in your own music library depending on genre, tempo, etc... STEREOMOOD.COM is even AWESOMER because it has playlists of songs that you may or may not be familiar with that are categorized by mood. I find this website loads of fun and was shocked that some of the ready-made playlists listed happened to match some that I have made in the past based on what I was feeling... Check it outtttt :)