If overshare is your middle name and you want everyone to know what song you are currently listening to and your top 10 weekly artists then you NEED Last.fm. Last.fm is a social sharing website with any number of ways to grab what you are currently listening to. Some people have their weekly top artists share to Twitter, the Blog, and/or Facebook. Last.fm is also a great way to discover new music because the Recommendations are based on what you've been listening to.
If you prefer music that doesn't come through headphones the Events feature in this app is a great way to discover what's happening in your city music wise. Imagine that - music in.real.life!