jquery bookmarklet – add jquery on every site you want
javascript:var s=document.createElement('script');s.setAttribute('src','http://jquery.com/src/jquery-latest.js');document.getElementsByTagName('body')[0].appendChild(s);
javascript:var s=document.createElement('script');s.setAttribute('src','http://jquery.com/src/jquery-latest.js');document.getElementsByTagName('body')[0].appendChild(s);