One device that is pretty hard to find in most computer hardware stores is one that allows you to take a 3G cell signal from a tower (you know that signal you pay about 60 bucks a month for) and convert it into a standard 802.11 Wifi signal that anyone you want can use.  This unit, commonly referred to as a mobile broadband router, is a good way to cut down on your cell phone data plan bill.  Also, imagine being able to carry a portable wifi halo around wherever you go.