Often times I’ll have a YouTube video playing while I use my computer. I’ve made a bookmarklet to open the embed version of a video which removes a lot of the wasted space on the page so that I can keep the window in the top right corner of my screen. You can use it by dragging the link below to your Bookmark Toolbar. When you click the bookmark, it will pause the current video and open a new window at the same timestamp in the video.
Edit: Updated to auto play video.