external_links_jquery.js

// http://www.learningjquery.com/2008/08/quick-tip-dynamically-add-an-icon-for-external-links
$(document).ready(function() {
  $('#extlinks a').filter(function() {
 return this.hostname && this.hostname !== location.hostname;
  }).after(' <img src="/images/external.png" alt="external link"/>');
});