For all of you on Itunes, I highly recommend activating the Genius functions. You'll need to grant Itunes access to scan your library to catalog the music not purchased through Itunes. After the inventory is completed, you can select any song in your library and the Genius function will create a playlist of songs with a similar feel and mood. I LOVE IT! With a library of over 50G of music, it's always pulling music I haven't heard in a long time or for that matter knew I had. The last song I heard was one I recognized from a recent movie that I did not realize 1. who performed it and 2. that I already owned it. A fun surprise.
The playlists generated are save-able. The Genius function ROCKS for a gal who likes to soundtrack her life. Try it out!