Topping the list of pry-if-from-my-cold-dead-fingers items would have to be my Nuvi 660 GPS unit from Garmin. There are many ways to get usable GPS directions on your truck, including standalone units from Magellan, Tom-tom and others as well as add-on software and hardware like Microsoft Streets & Trips, Delorme, and Co-pilot. No solution is perfect, but I consider the Garmin standalones to be head and shoulders superior to the others for the following reasons:
1) The unit itself is compact and light -- it fits on my dash easily, plugs into one of my DC sockets below. That's it. No laptop, no extra cabling, nothing. The display is extremely bright and can be seen easily under all conditions. At night it can dim itself and the user can select a range of brightness levels for day and night time.
2) The unit is almost shockproof, with no moving parts. Laptops have easily-busted hinges (for the screen), fans and of course hard drives. The read/write heads in a hard drive hover .001 of an inch off of the platters so every bump you encounter going down the road gouges the surface of your hard drives and will eventually cause data corruption and/or loss.
3) If you miss a turn the unit detects this in a few seconds and automatically recalculates a route from the new direction you have chosen. Some other units require you to hit a key, which isn't always possible in the midst of missing important turns in heavy traffic.
4) The unit speaks in dozens of different voices (and languages). Approximately one minute before each turn it will say something like "In one mile, turn left on Telegraph Canyon road, then stay right." As you get closer it briefly repeats critical turn information so you rarely even have to look at the unit.
5) The unit is bluetooth compatible and has an enormous database of the millions of businesses in the US. It will interface with your cell phone such that if I'm somewhere and want to order a pizza, or check movie listings or the like I look up the closest pizza joint and it automatically dials my phone with the number with the push of a button.
There are some limitations for truck drivers, most of which are shared by every GPS unit and program. First, the map database is never completely up to date so occasionally you will be sent down a road that has been closed, or turned into a one-way street, or the like. Just make a turn and it will recalculate on the fly and navigate you around the issue.
Second, it doesn't attempt to cover truck routes, low bridges, hazmat routes or the like. If you are hauling hazmat, for instance, you will still need to navigate around some cities by hand. However, it will recalculate every time you make your own turns so this really isn't a big deal.
Third is the cost. I purchased mine for about $700 at the start of 2007 (it is probably $100 or more less than this now). If you already have a laptop, adding on a simple program like Streets and Trips will run you about $100, and they include the GPS receiver you will need to plug in. But, see point #2, above, about durability issues.
I still occasionally miss a turn or get "lost", but with the Garmin I don't sweat it so much. The unit will figure out a way to correct the problem so as long as I keep my eyes open for low bridges and the like it works spectacularly well.
