Well, I'm at 3 sites, MySpace, Soundclick and ezfolk (
http://ezfolk.com).
I started with MySpace about 2 years ago and it does have many negative sides to it. And yet I still get the impression it's where people listen most and also where most musicians are. I had no idea they were dominated by the Hip Hop Scene! I met many musicians who don't do Hip Hop, but Pop/Rock, Folk, Chanson, Jazz etc. There are no restrictions as far as I know. By now you can upload as many songs as you like. As far as I'm concerned it's a nice way of getting into touch with like-minded people. So I put the negative sides aside and concentrate on the good ones.
On Soundclick I do have the impression that there are many Hip Hop people and I also find it quite complicated to navigate. I always get lost...but well, it's another chance of being heard.
Finally Ezfolk is ok for Folk and Singer/Songwriters. There are mostly American people who do Folk songs, and many who play ukulele. Other genres are welcomed but you get a bit lost/forgotten because there are so many ukulele players out there. But they are all very friendly and open-minded. It's quite a small place but it's like a family with a nice, cosy atmosphere (which is quite the opposite of MySpace).
Cheers,
Annika