You can import your existing iTunes library into Mufin Player Pro and it will analyze your songs using 14 different data points and then display them in a 3D visualization that groups them according to type. You can further organize tracks by sound type, like "heavy bass" or "rhythmic" and play them by simply selecting the track's point in the visualization.
Mufin Player Pro can also find duplicate tracks using its sound-based algorithm, which is pretty handy for people that might have libraries with only partial ID3 tags.
From within the Mufin Player, you can also access song recommendations from Mufin.com and share your listening data over Twitter, Last.fm and Facebook. If the track is in Mufin's database, it will be included as a link so your friends can listen too.
You can also share the playlists you create (using drag-and-drop) directly from the application.
Check out this video to see the Mufin Player in action:
Mufin Player Pro is $29.99 but a free version, without the 3D visualization and advanced organizational features is also available. The free version will also show you recommendations and let you share your songs with your friends.