The Google AdSense blog announced new referrals available for you to begin earning money. If you refer someone to install Google Pack you will get $2 each time, and if you refer someone to install Picasa you will earn a $1 each time.
You can use text links or graphic links for referrals. Here are examples of the graphic links in action.
On April 5th Google added AdWords referrals, on March 3rd Google increased referral period to 180 days, on November 29, 2005 AdSense allows Firefox referrals for International users, on November 4th 2005 AdSense opened the Google referral program, but before that, they had an invite only Google Affiliate Program on February 2nd 2005.