Mp3.com is back only it’s been bought out by download.com and has a fancy new interface. It’s in beta right now but you can go and sign up and get your artist name locked in before everyone else.
You’re limited to 50MB per artist, but you can have as many artists as you want – though they say they’ll kill any duplicate names (i.e. No Method, No Methods, etc) if you attempt to gain more space that way.
Right now you can only put your songs up there to be downloadable. There’s no streaming option since they’re still working out the kinks.