Firefox bookmarklet to get the current page's short URL, if one is defined. If no short URL is defined, gives you the option of getting one from TinyURL instead.

tiny.js

(function(){
  var promptURL=function (url){
    window.prompt("Copy short URL to clipboard:",url);
  };
  var links=document.getElementsByTagName('link');
  for(var i=0;i<links.length;i++){
    var tag=links[i];
    if(tag.getAttribute('rel')=='shorturl' || tag.getAttribute('rel')=='shortlink' || tag.getAttribute('id')=='shorturl' || tag.getAttribute('id')=='shortlink'){
      promptURL(tag.getAttribute('href'));
      return;
    }
  }
  if(document.getElementById('shortenurl')){/*Shapeways support*/
    promptURL(document.getElementById('shortenurl').children[0].value);
    return;
  }
  if(window.confirm("No short URL for this page found. Create one at TinyURL?")){
    document.location='http://tinyurl.com/create.php?url='+encodeURIComponent(location.href);
  }
})();