My old favorite, and often plugged service, LAUNCHcast has been renamed to Yahoo! Music since the last time I hit their homepage. It still rocks.
And, you really need to keep checking it out, because I know something you don't and it's gonna blow your mind when this goes public. Trust me, this is much(!) bigger than when I told you Barry Manilow was going on tour months before you heard it elsewhere.
Now, if only they would fix the service so it could play via Firefox...
By request, here is the link to Firefox.