AdSense has added two more products to the lineup of products and programs publishers can earn money from. Google Pack and Picassa are the two latest additions.
You’ll earn up to $2 for each time a user installs Pack and up to $1 for each Picasa install. Although Picasa referrals will be available for several AdSense languages, Pack referrals are currently only offered in US English.
As per the AdSense Policies, you can add one referral button per product per page, so you can now make a page extremely ad heavy just by using various ad units, link units, and referral buttons from AdSense.