Slightly off topic but was reading a review of the Samsung Note 2 (looks like a great device if you can live with its size) and saw the following mentioned, which I thought was nice feature!
"Arrange your music by moods
The music player of the Samsung Galaxy Note 2 features a fun little extra called Music square. This scans through your music library, arranging the tracks by mood - passionate, calm, exciting, joyful or a little in-between. Tap a block in the 5x5 square grid and you'll be greeted with a tune to match your mood."