With luck, you have found this site via either my original Stompbox How-To or the article I wrote for Make: Magazine. I've put up these pages under the stompboxnetworks.com name as the original URL (moro.fbrtech.com/~tora/EVDO) was rather ugly. All the old project pages are mirrored here now.
If you just wandered in here from a web-search or a curious click, you may be wondering just exactly what a 3G/Wifi StompBox is. A Stompbox is a home-brew WWAN (Wireless Wide Area Network) router. In more human terms, it's a compact little box that gets data from cellular towers and re-shares it for multiple computers to use.
To use it all one does is plug it in to the cigarette lighter of a car (or a 12v supply when at home). It automatically boots up and links in to a cellular data service, turning itself into an access point. Turn on your laptop, join the network and voila -- you're on the net! It's just like using a hotspot (such as they have at Starbucks and airports), but it goes anywhere you car goes. Some people have even hauled them around in backpacks to make themselves into a walking network access site.

The Stompbox 3G to WIFI hotspot