Yes there are some. You have the 2 main big ones which are AffiliateWindow and Tradedoubler. While approving listings for an affiliates directory I work for, I have come accrossed a few more in the past, but can't quite remember what they are called. They should be in the affiliates network category, but they would not have as many merchants as the first 2 I have mentioned. So they are the main 2 you should look at getting into.