ExchangeRate-API - An easy to use, free & reliable Exchange Rate API trusted by tens of thousands of developers since 2010!
ActTrader - ActTrader - The leading edge of currency trading technology
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.
FairFX - The easy way to manage your travel money online! Join the UK's smartest travellers. Spend abroad with a FairFX Currency Card in Euro, US Dollar or Sterling.
xChangeApi - Easy to use, free live updated foreign exchange rates API
TheBooks - Futures Trading and Accounting Software for CTAs, Hedge Funds, and CPOs.