Zorro!

CinemaDrape helps you focus on your current task on screen, by instantly blanking or dimming the other less important areas in a web page or in the background windows. CinemaDrape works anywhere and can help you write an important document, watch an online video, compose an email, or play a browser game. Use CinemaDrape to stop getting distracted by all those side elements, ads, or social network and instant messaging notifications. With CinemaDrape you no longer have to manually clean up your working screen area, close windows, or watch lower resolution videos in full screen mode just to get rid of the disturbing elements. CinemaDrape is very easy to use: adding a new transparent focus area is like drawing a rectangle. You can add as many focus areas as you need. And you can easily move or resize the focus areas using the mouse or arrow keys, save them for future reuse, pause or resume the drape, or change its color and opacity. »

TunnelVision allows you to hide the parts of the screen where your mouse cursor is not, effectively increasing privacy (though at a cost).

A program that darkens the whole Screen, except an user-defined area (which may include a video) for keeping the contrast if the background is too bright. It also works with several Screens.