Pay Per Play Ads

Anybody know of a good Pay Per Play network? I haven't found any that say how much they pay. One of the big music download sites, usershare, uses pay per play but I'm not sure which network they use.

Have any of you had success with PPP ads?

SellingPPP is probably the best one. I don't think it tells you how much they pay for each visitor but i am guessing it wont be very much