AdSense has announced that they are expanding the previously closed beta Referrals 2.0 program to be available to all AdSense publishers. This newly expanded Referrals is going to take a while for publishers to get their heads around but the basics of the expansion are that now instead of only being able to recommend and earn money from a handful of Google related products that you’ll now be able to refer your readers to thousands of products on a CPA basis (ie you get paid when your reader takes some action specified by the advertiser (like buy something).

Check this out:

http://www.problogger.net/archives/2007/06/29/adsense-launch-referrals-20