I've been active in several affiliate programs, the 2 that seemed to work the best is the affiliate recruiters program offered at reporting.net and goclick.com's affiliate program. I've received checks from both parties.

With reporting.net, I built a flash designed banner, you will notice it being offered when you log into your affiliate recruiters reports/add links account. The reasoning behind this, the banner size, layout, and what it physically has content wise will dramaticlly effect click throughs. I'm running another test with them on the oppisite side of the coin with a small button banner. My results so far, "don't bother with the buttons" the click through percentages are dismal compared to the larger ones, especially compared to the flash designed banner I created.

With goclick.com, I like the fact that they don't pester people everytime they hit the site, but the results aren't exactly accurate. I get a couple K of hits to my site daily, yet only get credit for a couple of hundred at most. It pays, and nothing to scoff at, but with both programms, plan having a ton of traffic to get anything worthwhile out of them.