I’ve been a Turntable.fm addict for the past 6 months. Right now it’s limited to US users only. It’s like IRC, but you “DJ” and play music for your friends. You can read more about what it is on the Turntable.fm About page.
I have a post-rock, post-metal, math, and sometimes shoegaze room called Post-rock & Beyond if you are a post-rock fan, stop in and discover new music. My username is MashTheSandwich.