Google Checkout is now offering subscriptions for sellers who wish to offer them. The option is available through the Beta Features page. Merchants can set up recurring billing through the API as well.
If you're not familiar, Google Checkout offers shopping cart functionality in a way similar to PayPal, which is owned by eBay. In April 2007, eBay teamed up with Yahoo to challenge Google Checkout, part of the ongoing search wars.
Last October, Google Checkout allowed multiple items per purchase. Recently, Google Checkout announced a new (higher) fee structure that will be in effect this May.