the one i know is referforex.com which is really a good affiliate with cool widgets and tools to help in promotion.
I've successfully used about 30 to 40 different programs.. from cpalead to hydra to maxbounty to cj to clickbank, and on and on. If you name it, I've probably used it at one point or another, if only for a test/trial run to get a review up on cashbackaffiliates.
Obviously, nobody is going to share a successful merchant or product with you but all the major networks work well. I just posted about prosperent which is a newer player in the affiliate game. They have a couple real advantages. First, since they work with CJ, SAS, Linkshare, etc, and all the merchants in those companies. Second, they match what the user was looking for when they searched which gives you a much better chance of a potential match and sale. I would check it out as it is a pretty easy way to get started and gives you a one-stop that can give you matching products for every niche.