ValueClick Media · Has many offers that can make you money. Lots of text links as well as banners. And co-branded sites to make your site look great.
LinkShare · Partner with over 500 of the web's top merchants. Earn revenue for sales, leads, and traffic driven from merchant links. Very well organized and good reporting.
Commission Junction · Choose from a large network of leading retailers. Lead or sale based. No minimums per merchant, Commission Junction sends check monthly based on your totals for the month. Good reporting.
Share Sale · Find a sponsor for your web site. Assortment of small sites to link to.
AllPosters.com · They have a large assortment of posters and art. Good plan with high payout and easy link set up.
Performics - Connect Commerce · Connects distribution partners with top-tier online clients. You'll receive a commission or bounty for the sales and leads generated. List of clients include Discover Card, Eddie Bauer, Orvis, Hammacher Schlemmer, Spiegel, and Bose.
cyberbounty · Has a pretty good reporting system and some good advertisers. Add banners of your choice to your site and/or they can automatically serve banners to your site.
VMC Satellite · Get $50 for each person that orders a free satellite dish.
Free-Banners.com · Sort of a link exchange program, but you can make money from it too. Worth looking into to see if it fits with your site. Here is what the banners look like: