There are several applications available that will help find a lost or stolen Mac. Here at TUAW, we've talked about LoJack for Laptops, Orbicule's Undercover, MacPhoneHome, and iAlertU from Slapping Turtle. Most of these apps "find" the computer by determining the IP address of the machine, and using that data to narrow down the physical location where the laptop is in use. That information can be shared with police and ISPs to find the thieves, recover your laptop, and make an arrest.
There's a new Mac recovery app available called MacTrak that's different -- it uses the same Skyhook Wireless positioning technology used in the iPhone to accurately determine the location of your Mac within 10-20 meters. If your nice new MacBook Pro is lost or stolen, you simply log into a special web page with your predetermined credentials, and click on one button to start tracking your Mac. Every 30 minutes, MacTrak takes a picture with the iSight camera, then sends detailed information including its latitude and longitude to you via email. At the same time, it uploads that same information in a "Wanted Poster" view to your Flickr account. You can then work with the proper authorities to have your Mac returned to you. Read on for more info about MacTrak.