As some may have already marked it, we have now added for a few days already now a blog system to the forums. There you can upload your own music for everyone to hear it, have your own blog too, customize the place (blocs can be moved around, modified, added…) and there's more in the works
Moreover IT'S FREEOf course, if you just want your MP3 to be uploaded and streamed from here, you don't have to use the blog itself, though you'll have to open the blog, but no-one will force you to post anything, it's a free country.
And last, you retain all the rights to your own music!
To access the blog/MP3 player, start the service by using "my controls" then start the Blog in the left column. (from memory, sorry if I mix things up)