I have always envied CSI's amazing IP address geolocation capabilities.
Not only can they get your exact physical address based solely off your IP (right down to your hotel room number!), it even works on IP addresses that don't exist!
While that level of IP address tracking is beyond the grasp of us mere mortals, MAC address geolocation provided by Google Location Services is pretty close. Just feed them the MAC address of your wireless router and they will tell you, with scary precision, where you are.