Watching YouTube while you're working can be difficult! Video takes up valuable desktop real estate, so Double Vision has been created to solve the problem.
Essentially, Double Vision is a browser that will maximize video content on popular sites, and then play them on a transparency layered on top of whatever you're working on. So if you open a YouTube video, click the Double Vision button, and it will become translucent, allowing you to see your work underneath and the video too.
For major sites, and most video files on your PC, this works fine. There is unfortunately no way to set up video playlists, so your video watching will still interrupt you in between shows. The biggest problem with Double Vision is that it is a browser, but not a very powerful one. There are some streaming services that don't work, and Double Vision can't accept the correct plug-in. This is even true with Adobe Flash, which is a really common necessity.
Despite these weaknesses, and its slightly resource hungry nature, for YouTube addicts and on many other sites, it works fine.