I have added an article about my PAWS Marketplace example application to the AWS resources site: PAWS Marketplace - A Rails Marketplace Application in the Cloud.
The PAWS Marketplace is a proof-of-concept Ruby on Rails web application that runs entirely on Amazon Web Services. The application’s web site allows anyone with an Amazon Payments account to buy or sell digital products, while the marketplace’s owner earns commissions for the sales it performs. In addition to serving as an example marketplace implementation, this application is interesting because it uses the SimpleDB service to store its data instead of a traditional relational database.
The article describes how to install and run the marketplace web site yourself. It also includes links to the example code, and to a screencast video that demonstrates how to configure and use the marketplace web site.