How do you use the internet on my laptop in the car?

Mostly for checking Mapquest.com and Google Earth to see if you know where you're going, so we don't get lost.
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*hangs head* Sorry, couldn't resist.

Check with your local cellular providers to see what mobile broadband services they offer and where they offer it. Then subscribe and purchase a compatible USB or PCMCIA card to insert into the laptop. Portable satellite systems exist as well ($$).

This Connecting my laptop to the internet in the car post discusses hot-spot hopping as an alternative.