Apply to become a member of the and you will earn $20 for each customer who signs up for AdWords or AdSense through your site.

The Google referral program (beta) is for businesses whose customers and visitors include small to medium-sized businesses, and who want to help those companies become more successful by running Google AdWords, or serving ads with Google AdSense. The program works by giving approved sites unique links to Google, then compensating the referring site for passing on a new AdWords advertiser or AdSense publisher.

From Google:

What You Should Know About the Google Referral Program

How the Google referral program works:

1. Complete the online application form.
2. Agree to the terms and conditions.
3. Submit the form to Google for approval.
4. Google reviews your application. Upon approval, Google sends you a welcome email with your setup information.
5. Google emails you the appropriate logos, links and HTML code.
6. Place HTML code, links, and logos on your site. The HTML code lets Google track your referrals.
7. Review your progress and revenue in the program's monthly email reports.

How you get paid:

1. One of your visitors clicks on the graphic or link and is taken to a Google sign-up page.
2. That person signs up for an AdWords account or applies to become an AdSense publisher.
3. Advertisers qualify as completed referrals after they spend $20 with AdWords. Publishers qualify after they earn $75 in AdSense revenue.
4. Every month, Google calculates the number of completed referrals you have directed to Google.
5. Once you accrue $100 (five completed referrals) or more, you will receive a check. Google only issues checks once a month (for details, see the FAQ).