The ChargeOver Python SDK by ChargeOver allows to access data from the API to integrate automated billing and payment services into applications. Documentation includes REST API, webhooks, and example code.
Dwolla is an extremely innovative Payment API and the site allows you to transfer money with one of the least payment charges. We have covered Dwolla before here. Here is an interview with Michael Schonfeld, Developer Evangelist of Dwolla API.
Verifone, a payments and commerce solutions provider, has announced that the company is leading an effort to define and implement the Conexxus Mobile Standard, a new Mobile API standard that aims to coordinate interactions between mobile payment and loyalty program applications.