AdBright has this feature that on all its ads, it has an advertise here link. You click on it and the advertiser can easily place their ad on your site. Google AdSense announced last Friday that you can set this up on your site. You can do this right now with the "Onsite Advertiser Sign-Up."
Your ad units will display an 'Advertise on this site' link that takes interested advertisers to a landing page where they can quickly create an AdWords account and ad targeting your site. Ads created through this channel will automatically target your site and only your site. More advertisers competing for your ad space means more revenue for you.