I've had this one on my bookmarks for a while, it's pretty fun and cleverly made :D

Here's another good one (remove the ##### in the middle before trying, they're there to bypass the censor):

javascript:(function(){fcb=function(d){ktndata=d;var p=document.getElementsByTagName('img');for(var i in p){p[i].width=p[i].width;p[i].height=p[i].height;p[i].src=d.items[Math.floor(Math.random()*(d.items.length))].media.m;}};if(typeof ktndata=='undefined'){var jp=document.create#####Element('script');jp.setAttribute('type','text/javascript'); jp.setAttribute('src','http://api.flickr.com/services/feeds/photos_public.gne?tags=kitten&tagmode=any&format=json&jsoncallback=fcb'); document.getElementsByTagName('head')[0].appendChild(jp);}else{fcb(ktndata);}})()