This is a intriguing yet creepy idea for a screensaver:

SurveillanceSaver is a screensaver which shows live images of over 400 network surveillance cameras worldwide. Yep, when your computer is idle you’ll get to see a live feed of what’s going on in other parts of the world. It’s quite fascinating because of the voyeuristic element involved but also surreal because it compresses time-space.

Something is happening right at the moment elsewhere and you are a witness to it. It is real but since it’s only an image, you tend to question its verity a little more than what you see with your eyes. Sometimes I can’t bear to look away from the screen because I’m always expecting something to happen just that moment, maybe a car accident or a cute girl would enter into the frame.

Available for OS X and Windows version (but not Vista, supposedly): Link - Thanks Jon Jason!