WidgetBucks – does the heavy lifting by creating contextual ad widgets that your visitors will actually find interesting and engage in. You reap the rewards of PPC ad widgets that earn better than $2 CPM. WidgetBucks also offers the Referral Program, in which affiliates can earn a 15 percent referral fee based on the commissions earned by the people they refer. Payouts are monthly and paid along with commission checks.
AdBrite - Generate more revenue from your ad space. Adbrite offers customize ads to match your site, approve and reject ads for your site, works alongside with other ad programs, and supports: text ads, inline ads, banners, britepic, and fullpage ads.
Google Adsense - free program that enables website publishers of all sizes to display relevant Google ads and earn money. Great program for beginners and learners, offers in-depth analytics.