Alright, so it's not free software (Trial version available) but this sweet little program allows anyone with a laptop to use it as a second monitor.

According to the blurb, it installs a virtual VGA adapter, then transmits the video output via your network to the laptop.

http://www.snapfiles.com/maxivista.html

Anyways... I thought that was pretty smart. Make the most out of the quality screens on laptops when they're just sitting around.