Explore music!
I know there are quite a lot of services that allow you to upload data on the music you're playing. Often you can then go and look at wht other people are listening to. Find peers in musical taste. Even listen to their music. iLike is such a service, but the integration of their iLike client into iTunes is just smashing.

App name: iLike

Developer: iLike
Promotion in podcast: no (freeware)