http://adeona.cs.washington.edu/

Installed, this program will help you track down your missing/stolen laptop or desktop. Adeona runs in the background, and works its magic by waking up at random intervals to record data about the equipment’s location and status, which it encrypts and then silently uploads to off-site storage. If your laptop (or, for that matter, your co-located server) goes missing, you can retrieve its latest records from elsewhere, learning such information as its internal and external IP address, local network configuration, and more. Armed with that info, you can call law enforcement and drastically increase the chances of recovering your laptop. If you have a mac, it can even snap photos of the person using your computer, with the built-in cam.