Google has introduced a new program that allows AdSense publishers to garner fees for referring users to Google. Publishers add a referral button to their site that directs users to sign up for AdSense or download the Firefox browser with the Google Toolbar. If a referral signs up for AdSense and earns US $100, Google will credit publishers with a US $100 referral fee. If a referral downloads and runs Firefox, publishers receive up to $1.
More information on the new program can be found here.