Active Merchant is a simple payment abstraction library extracted from Shopify. The aim of the project is to feel natural to Ruby users and to abstract as many parts as possible away from the user to offer a consistent interface across all supported gateways.
Serve is a small Rack-based web server and rapid prototyping framework for Web applications (specifically Rails apps). It is designed to compliment web application development and enforce a strict separation of concerns between designer and developer. Using Serve allows the designer to work in a separate prototype project, while the developer can work on the actual application and utilize resources from the prototype as needed. This allows the designer to focus on presentation and flow, while the developer can focus on implementation.