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.
XE.com - XE.com Inc. (XE) is a Canadian online foreign exchange services company.
exchangeratesapi.io - Foreign exchange rates API with currency conversion.
Tweetbot - Sync your timeline across your iPhone, iPad, and Mac. Mute tweets by user, hashtag, tweet source, or keywords (including regex). 3rd Party support for image, video, read later, and timeline sync services.
xChangeApi - Easy to use, free live updated foreign exchange rates API
Yahoo! Finance - Currencies Center - Currency Converter from Yahoo! Finance.