Simple Currency Converter is a WordPress plugin by vjekonikolic that adds a widget for simple currency conversion. Utilizes AJAX for smooth experienece.
Data is fetched from Yahoo! Finance web site per each request, making it up-to-date every time.
Requires WordPress Version: 2.0.2 or higher Compatible up to: 3.1
Download and info: http://wordpress.org/extend/plugins/simple-currency-exchange/