I love Gmail, it simply gets more useful every day.
If you have Labs enabled in your Gmail account, you can now display your location information at your signature. You’ll probably find this useful if you are a frequent traveler.
First, you have to enable the “Location in Signature” feature in Labs, and then you have to enable signatures under settings and check the box in front of the “Append your location to the signature” option. After these steps, Gmail will use your public IP to locate where you are.
It says on the Gmail blog that using Google Gears with location module brings more accurate results with Wi-Fi triangulation.