Fixer.io - Fixer provides a free, simple, and lightweight API for current and historical foreign exchange rates and currency conversion. The API tracks rates published daily by the European Central Bank.

ExchangeRate-API - An easy to use, free & reliable Exchange Rate API trusted by tens of thousands of developers since 2010!

exchangeratesapi.io - Foreign exchange rates API with currency conversion.

xChangeApi - Easy to use, free live updated foreign exchange rates API

Cambridge ePayables Solution - Cambridge ePayables Solution is an electronic enablement process that assists companies in the reduction of traditional check payments, and is supported by technology that allows the business partners to efficiently enroll their payment details in a…

Open Exchange Rates - Free, hourly-updated exchange rates - a simple, accurate, open-source JSON API. Free for personal use, a bargain for everybody else.