shopping cart code and digital downloads

A google ad on this very blog pointed to www.fatfreecart.com which looks pretty useful. Free shopping cart code for google checkout and paypal. Of course, many hosting companies offer free shopping cart code with their hosting too... And DigiVendor seems to be a useful MySql-Php secure downloads payment option. The Google Checkout API docs detail the process, and provides sample code, too. Similar stuff exists for paypal.