I have not tried this, but I think porn mousepads would sell.
Actually, not sell them, but instead, give them away for free...
all surfers pay for is "shipping and handling"
Might be some good extra $$$ in that as an exit console ad.
When they are leaving after not buying a membership, hit them
with a "free" offer of a sexy mousepad, and maybe squeeze
that $6 - $8 or so out of them.
Just a thought
I've never have much luck selling products other than penis
pills, some AdultFriendFinder memberships, and the occasional
dvd or sex toy.