The number of affiliate networks continues to grow. Competition rages between the top 3 affiliate networks Commission Junction, LinkShare, and Performics. Share A Sale has found a good niche targeting smaller to medium size merchants. There are still more networks such as Affiliate Future, which offers many merchants including the great eBook by Vlad, "Practical Guide to Affiliate Marketing" and still more affiliate programs are run in-house or by emerging affiliate networks. Here is a run down of the top four affiliate networks.