My wife noticed something pretty cool in Google Maps. This morning when she was about to head out to the BlogHer conference, she wanted to get directions to the Hyatt. She entered the address in Google Maps, and then clicked on the Directions link, and it gave reasonable directions.
The interesting thing about this, was that she wasn't logged into Google's services, so it didn't know our address. It looks like Google estimates the location of the ip address of the client, and uses this as the originating location.