Ridiculously simple live currency conversion. I will make it into a jquery plugin soon but for now, if you put the convert.js snippet inside a jquery document ready tag it should just work™.

convert.coffee

if $('span[data-currency]').length > 0
  $.get '//query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22EURUSD%22%2C%20%22EURGBP%22%2C%20%22EURJPY%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=', (result) ->
    $('span[data-currency]').each ->
      matches = $(this).data('currency').match(/(\d+) (.+)/)
      amount = parseInt(matches[1])
      conversion = matches[2]
      for conversions in result.query.results.rate
        if conversion == conversions.Name
          rate = conversions.Rate
          return $(this).text Math.floor(amount * rate)

convert.js

if ($('span[data-currency]').length > 0) {
  $.get('//query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22EURUSD%22%2C%20%22EURGBP%22%2C%20%22EURJPY%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=', function(result) {
    return $('span[data-currency]').each(function() {
      var amount, conversion, conversions, matches, rate, _i, _len, _ref;
      matches = $(this).data('currency').match(/(\d+) (.+)/);
      amount = parseInt(matches[1]);
      conversion = matches[2];
      _ref = result.query.results.rate;
      for (_i = 0, _len = _ref.length; _i < _len; _i++) {
        conversions = _ref[_i];
        if (conversion === conversions.Name) {
          rate = conversions.Rate;
          return $(this).text(Math.floor(amount * rate));
        }
      }
    });
  });
}

currency.html

€500 is $<span data-currency="500 EUR to USD"></span>, £<span data-currency="500 EUR to GBP"></span>, <span data-currency="500 EUR to JPY"></span>¥

output

€500 is $681, £415, 71226¥

As promised, here is the jQuery plugin http://github.com/johnrees/cambio