The Balanced iOS SDK by Ben Mills allows API communication with the aim to implement credit card and bank accounts into applications. Usage includes code to create a marketplace project, create a card, and create a bank account object.
Celery, flexible ecommerce solution provider, allows users to accept pre-orders without charging the customer until the product is ready to ship. On the flip side, customers also have the capability to pre-pay for goods and services. In addition to flexible payment options, Celery allows developers to integrate its functionality with third party apps and workflows via the Celery API.
Microsoft's latest version of its search API (our Live Search API Profile), which was released last November as a public beta, seems to be gaining quite a bit of momentum. According to a recent post on the Live Search Blog, the API is serving more than 3 billion queries per month, more than 5,000 applications to use the API, and queries from third party sites account for 80% of the API's query volume.