Load JavaScript Asynchronously. Usage: _async('//example.com/script.js', 'dom-id'); Taken from Twitter and Facebook widget loader scripts and altered a little bit. :-P

gistfile1.js

/**
 * Load JavaScript Asynchronously
 *
 * usage: _async('//example.com/script.js', 'dom-id');
 */
function _async(src, id) {
  setTimeout(
    function(d, s, id) {
      var js, fjs = d.getElementsByTagName(s)[0];
      if (d.getElementById(id)) {
        return;
      }
      js = d.createElement(s);
      js.id = id;
      js.src = src;
      fjs.parentNode.insertBefore(js, fjs);
    } (document, 'script', id), 
    0
  );
}

gistfile2.js

// Minimized.
function _async(src,id){setTimeout(function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(d.getElementById(id))return;js=d.createElement(s);js.id=id;js.src=src;fjs.parentNode.insertBefore(js,fjs);}(document,'script',id),0);}

_async('//example.com/script.js', 'dom-id');