Adsense now offer refferal program. You can earn more when your refferal earns.
When a publisher that signed up for AdSense through your referral earns their initial $100.00 and is eligible for payout, we’ll credit your account with $100.00.
You can get the refferal code under Referrals tab. The refferal buttons will look like this:
The only problem with those buttons are they are a little big. I mean if you allready have a big add banner on your site allready, you don’t really want that aswell!
Ya… they do have small one.. but not really small. the smallest size they have is 110×32