Laptop Cop, which lets you remotely control your computer and delete files if it is stolen, now has a geo-location feature based on WiFi-hotspot triangulation technology from Skyhook Wireless. It is the same technology that is used in the iPhone (along with GPS and cell-tower triangulation) to determine your location for geo-aware apps. Now you can tell the cops exactly what door to knock on.
check it out here.
Unfortunately it isn’t free. so if you just want to know where your laptop is you can download loki (here).