Ive been using these guys
http://www.4rx.com since 2008 and they have been awesome. Its a real nice thing to sell everyone wants it.
I tried someone else but sales dropped and went right back to 4rx and sales are good.
Most of my sales are with viagra and cialis, I havent pushed other stuff.
edit: forgot to link to their affiliate program:
http://www.4rx.com/affiliate-program.html