We’re happy to announce that, in addition to AdSense, AdWords, and Firefox with Google Toolbar, you can now refer your users to Google Pack and Picasa. 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.

To display Pack and Picasa referral buttons on your site, all you have to do is select Referrals from the AdSense Setup page of your account, and then select the product of your choice. And remember, now US English publishers can use text links for your referrals.

http://google.weblogsinc.com/2006/05/05/new-google-referral-options/