WWWAdverts
WWWAdverts is a system for maintaining a set of random banner ads display on your site. Banners're displayed on your pages with SSI or PHP calls. Multiple "Options" can be established, allowing certain banners to appear only on certain pages (with Keywords) or with the visitor's language. WWWAdverts keeps track of exposures / clicks for each banner, as well as of the average total number of exposures / clicks. And you can allow a sponsor to see stats of his banners (use a password protect).