I've used Chitika and Infolinks, as well. Just don't go overboard and load up your pages with this stuff. Search engines don't like it, and visitors don't particularly like it either.
Also, something that may help: One should attempt to align content with affiliate products. The more targeted the visitor, the more profitable the visit.
If you put irrelevant, generic ads on your site, the click through rate diminishes greatly. But if you offer products related to your content, and weave recommendations for those products into your copy, conversions will increase.
Placing ads in the same place over and over causes ad blindness and visitors won't convert. So you must experiment with ad placement to discover optimum performance.
Oh! And don't forget to put "nofollow" tags on affiliate links for good measure!