Put the code in a browser button. If you click it when watching a YouTube-video, the video will open in a pop up. Disctraction free and perfect for watching videos while "working".

Distraction Free YouTube

javascript:yturl=window.location.href;ytarr=yturl.split("?v=");ytqs=ytarr[1];ytqs=ytqs.replace("&","?");ytelem=document.getElementById("movie_player");yttime=Math.floor(ytelem.getCurrentTime());document.getElementsByTagName("video")[0].pause();if(ytqs.indexOf("?")>-1){ytqsstart="&"}else{ytqsstart="?"}window.open("https://www.youtube.com/embed/"+ytqs+ytqsstart+"autoplay=1&start="+yttime,ytqs,"width=400,height=300");void(0);