Common Name: imeem

Niche: music - social networking / social media webiste

Slogan: What's on your playlist?

What they say about themselves: "imeem is a social network that enables users to discover, interact and express themselves with media, including music, video and photos, and form connections based on shared tastes and interests."
What I say about imeen: Nice, focused primarily on music with lots of good music.  The community aspects include Battles and Pools where members vote on favorite tunes, artists and groups.  Clean simple interface and not too much advertising -- if you're into music, imeen is for you.

www.imeen.com