Yahoo has a YQL feature to get a whole bunch of currencies at once in XML or JSON. I've noticed the data is up to date by the minute where the ECB has day old data, and stops in the weekend.
http://query.yahooapis.com/v1/public/yql?q=select * from yahoo.finance.xchange where pair in ("USDEUR", "USDJPY", "USDBGN", "USDCZK", "USDDKK", "USDGBP", "USDHUF", "USDLTL", "USDLVL", "USDPLN", "USDRON", "USDSEK", "USDCHF", "USDNOK", "USDHRK", "USDRUB", "USDTRY", "USDAUD", "USDBRL", "USDCAD", "USDCNY", "USDHKD", "USDIDR", "USDILS", "USDINR", "USDKRW", "USDMXN", "USDMYR", "USDNZD", "USDPHP", "USDSGD", "USDTHB", "USDZAR", "USDISK")&env=store://datatables.org/alltableswithkeys
Here is their query builder, where you can test a query and copy the url:
http://developer.yahoo.com/yql/console/?q=show%20tables&env=store://datatables.org/alltableswithkeys#h=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20%28%22USDMXN%22%2C%20%22USDCHF%22%29
