Payage is a free Joomla Component that manages online payments via multiple payment gateways for multiple Joomla components. It has a well-documented API so is an ideal payment platform for any Joomla component.
Payage only deals with payments. It is not a shopping cart or a booking system. On its own it does nothing useful. But when used as an isolation layer between the application and the payment gateways, it makes the application code simpler and cleaner, and makes it relatively straightforward to add new payment gateways.
Payage was primarily developed for use by our own components, but it is free and open source so can be used by anyone to simplify the development of a component that requires payment interfaces.
Payage currently supports PayPal, Skrill (Moneybookers), PayPlug, Barclaycard ePDQ, Mollie, SagePay, WorldPay, and Offline (manual) payments. More will follow.
The developers guide describes how to build Payage applications and how to add new payment gateways.