CJ pro seems pretty good,
http://www.circlejerkpro.com it's free. Ive never used it...but I like trading with it. The stats and the returns seem pretty close to what Im showing on my end. 1% of your traffic goes to his site though...thats why it is free.
There is also CJ ultra...looks like a good script. Again...the free version sends 1% to one of his websites. (Im sure Lane or Shane will be here in a minute to give you more info. They are like Hawks looking for a meal!)
http://www.cjultra.com/