I used shareasale and Linkshare to build a site and did quite well for a few months, then someone caught on and my natural results dropped. I'm still over 2,500 visits / day - about half where I was.
Also, I'm trying ValidClick (overture) ads, instead of AdSense. Greater control over the presentation of the ads, but be prepared to be put through the ringer to be approved. I just started with them this month, but am only seeing 75% as much revenue than when I was with AdSense. I'll let it go for a bit longer, but am already thinking of going back.