I read a suggestion to mark out your route on a map, zip it in a ziploc (with route showing) and tape it to the fuel tank. Easy to quickly glance at it, and no high-tech gadgets to fiddle with.
(oh, no, I’m not turning into a luddite am I? no cable modem, no Ipod, no Blackberry, and now advocating use of paper maps! AAHHHH!!!)