jQuery.extend(
  jQuery.expr[ ":" ],
  {
    /*
      /:\/\// is simply looking for a protocol definition.
      technically it would be better to check the domain
      name of the link, but i always use relative links
      for internal links.
    */

    external: function(obj, index, meta, stack)
    {
      return /:\/\//.test($(obj).attr("href"));
    },

    internal: function(obj, index, meta, stack)
    {
      return !/:\/\//.test($(obj).attr("href"));
    }
  }
);