I have found that navigation by a handheld GPS gets a tad silly at times. Handheld GPS units are great for hiking, don't get me wrong, but for vehicle travel, I wanted something better suited. So I mounted the laptop on a ram-mount:
I run Delorme Topo USA (after reading good reviews from this site):
Here's a panorama from the passenger seat during a recent trip (taken while I was spotting some guys through a slightly rough spot).
After running with the mount through a few trips, I realized there are two needed upgrades for the ram system:
(Otherwise the screen vibrates everywhere and eventually bends over)
Low profile laptop holders:
(With the stock ram-mount holders, the screen cannot close while the laptop is in the holder)