Global Currency Updater
The Global Currency Updater is a native Salesforce.com application which allows updating the organization currencies with the latest converstion rate.
The Global Currency Updater is an easy-to-use feature developed using APEX classes and Visualforce page. The component can be easily added to any page in Salesforce.com and launched to update the dated exchange rate. It makes use of Yahoo web service to fetch the conversion rates of currencies enabled in the Salesforce.com org. Note that the multicurrency needs to be enabled for the organization in which this service is to be enabled.
The application is available for FREE and can be downloaded from here