Beginning January 1, 2008, when you use Google Checkout to process your sales, you’ll be charged a low 2% + $0.20 per transaction. With Google Checkout, there are no monthly, setup, or gateway service fees.
If you’re an AdWords advertiser, you will also be eligible for free transaction processing for some or all of your Google Checkout sales each month. For every $1 you spend on AdWords each month, you can process $10 in sales the following month for free through Google Checkout. This standard, non-promotional type of free transaction processing may be updated from time to time.
Non-Profits: Google Checkout is offering free payment processing until 2009 for approved non-profit organizations to accept donations online.