Article writing, Blogging, paid per click, the list goes on. My mentor taught me to be creative with what you do to market your affiliate program. I am trying all sorts of different things and it seems to be working. PM for more info
I would suggest you keep it up with PPC with adwords. But you should check out PPC-Coach and get a subscription there. They will help you out a LOT. Check out the link in my signature.