Current leverages the Open Exchange Rates API to create an ultra-lightweight, simple currency conversion display tool that's easy to use with your web application. The Open Exchange Rates API requires an API key, which you can procure here.
Show conversions on hover: $100.63
…or on click: $5.29
…or side by side: $37.50 USD
Set base and currency criteria directly from your markup: $99.99
Repo & docs available here.