The Amazon Product Advertising PHP Library by Jan Eichhorn is based on PHP REST and SOAP using the Product Advertising API. It is made to be flexible for using built in operations (such as Item Search) or implemented operations to fit developers' needs.
Groupon, which calls itself a "social commerce site," is one of many online services that help consumers pool their buying power to get great deals. However, few companies can share Groupon's experience of attracting $135 million dollars from the same venture capital funds that helped grow Facebook and Zynga. To help third-party developers and affiliate members get the word out about its daily specials, Groupon has released a publicly available API.
Payleven, the Square equivalent for the world outside of the US, has launched an API to complement its mobile payment device. Prior to the API, use of Payleven's mobile payment device required downloading the Payleven app (similar to Square's current model). However, the API allows developers to integrate Payleven's functionality within third party apps.