Cryptsy offers bitcoin and digital currency trading services. The Cryptsy Node.js library created by Ek Palmer contains an illustrated example to demonstrate a list of all markets that participate in trade events. What the API does for users is to allow the query of general market data and orderbook data. Additional information such as market data, transactions, and execution of trades is available with authenticated methods.
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.
Among the 25 finance-related APIs now listed on ProgrammableWeb, there are services from old and new and large and small companies. Overall, most current business and finance APIs fall into one of two categories: APIs from SaaS-based management services, and APIs that provide financial markets data.