Making Money On The Web Through Advertising
From DesigningPatterns
Google AdSense
With Google AdSense, you add a Google sidebar on your website, in which Google places ads. Google processes the content on your site to determine which ads to place. Each time a visitor on your site clicks on one of these ads (not sees the ads), the advertiser pays Google, and you receive a cut. The price paid depends on how high the advertiser bid to place those ads through Google AdWords.
Plenty of Fish, a dating site, is entirely funded by advertising (see article).
