Open Source Exchange Rates API
Earlier this week I came across an interesting API, called the Open Source Exchange Rates API. If you have ever tried to pull exchange rates to calculate something on the fly in your code, you know how hard this is as most APIs charge for the data they provide. The popular solution has been to, using some PHP magic, perform a Google search on the currency conversion through their search API, which works but is a little unstable and frankly a pain in the ass.
The Open Source Exchange Rates API works great though, providing a JSON formatted API which is easy to pull in and use in a number of programming languages. It is as you understand, fully free and also updated every hour with the latest currency data. On their website they have proper documentation on how to use the API.
