In Leopard, your Address Book doesn’t just tell you where to go—it shows you!
To get an instant map to any address, just control-click on the address field of a contact card (or right-click if you have a two-button mouse). Then select Map Of.
This command opens Safari (if it’s not already open) and reveals the address in Google Maps.
This trick isn’t just confined to Address Book: Leopard can detect street addresses within Mail as well. When your cursor hovers over a street address in an email, a dotted rectangle surrounds it and a small gray triangle appears. Click on the triangle and select Show Map... to see the address in Google Maps.