Google AdSense has released a program for all the AdSense publishers by which the publishers can earn $20 when they refer a new advertiser to Google. But for this the referred advertiser has to spend $100 within 90 days of sighning up. last year the program was available to ony a few publishers in certain parts of the world. But now its available to all the AdSense publishers.
More deatails about the program can be found at Jensen.