https://services.google.com/inquiry/checkout_ecommerce

If you are an e-commerce provider, here are a few of the program benefits you could be eligible for:

1. For one year, get paid for every merchant you sign up and earn a percentage of these merchants' Google Checkout sales.

2. Earn bonuses for integrating with Checkout – you can even earn an extra bonus for integrating before September 30th, 2006.

3. Gain free marketing exposure to merchants looking for e-commerce providers integrated with Google Checkout.

[via http://googlecheckout.blogspot.com/2006/08/bringing-google-checkout-to-e-commerce.html]

I integrated within 48hrs of it being released, maybe they can provide a link to me on google, that would be the best bonus.