Have you see that some Google Adsense ads are showing “Advertise on this site” link besides the “Ads by Gooooogle” link on the ad units. This is there new Onsite Advertiser Sign-up option… to help you make extra money quickly by getting advertisers.
The link from the Google Adsense units titled ‘Advertise on this site’ takes advertisers to an informational landing page with details about your site and the Google AdWords advertising program. Advertisers who sign up through this page will be guided to create an ad targeted specifically to your site only. When more advertisers create and target ads to your site, you’ll benefit from the competition as it drives your potential earnings up. Take their guided tour.
You can customize the landing page advertisers see with the logo, color scheme, and site description of your choice. Learn how to customize your Onsite Advertiser Sign-up page. If you run adsense on multiple website, you can customize one landing page only for each account and advertisers will access the same custom landing page from ad units on any of your sites. Although you cannot track them as yet, if advertisers are bidding on your site, you may notice more CPM ads appearing on your site with an increase in your earnings. So set it up now and and start making more money fast.
Update: This feature is retired by Google. AdWords advertisers will still be able to target your individual sites by using placement targeting.