ProAdult's
Quantum sells & rebills well, but they really limit you with what you can upsell within the site. For instance, you can't advertise any kind of paysite even inside the member's area.
I have my best luck with
FreeNetPass. The "free" passes are easy to sell & you make $15 a pop. The free site requirements are minimal & are very webmaster friendly - 10 pic minimum, very few restrictions on advertising, exit popups are allowed, etc.
The
FreeNetPass Premium program is also good. Free sites that are designed to upsell Premium sites get a "Recommended" designation and are at the top of the linklist & search engine results, and Premium site requirements are much more flexible & allow more selling opportunites than any of the other "Premium" AVS programs.
Both programs offer free hosting if you want it.