If I were just mentioning this site for the points, it wouldn't make the cut (and I have a very low bar for inclusion), given the price of the rewards. But it's actually a useful site. Sign up, type in the type of music you're looking for and it will give you a bunch of options, all of which are free. Right now, I'm rockin' to some new wave 80s. You get ten points automatically awarded to you every ten minutes, and if you want the points but not the music, there's no reason you can't mute it. It also has the standard "bonus offers" you can do for more points, but that's up to you.
One note: When you sign in, first sign in to the main site and then sign in again on the music page.
And yes, it does offer points for referrals. You earn 10% of whatever your referrals earn. Feel free to start a Conga in the comments. I'll probably never get a prize, but if I'm going to listen to the radio anyway, might as well earn points for doing so.
Feel free to sign up here.