Very good question. The only way I would know how to do it is through Windows XP Internet Connection Sharing. There is a setup routine to go through that allows a second (or more I guess) computer on a network to access the internet through the connection of a "host" computer. My wife and I used this on our home network four a couple of years before we got DSL and a router. It's a little aggravating to set up, but really worked well once configured.

Here is a link to a thread here weeks ago that addressed this issue. Our fellow AgTalker, 99guy, found this unit that will run a cellular internet to a router over a network; it uses a PCMCIA "modem" or card some way. It's a little pricey, but sounds competitive with satellite based internet in performance, price, and speed. Of course the speed is dependent on the availability of cellular internet in your area.