If you already have a laptop, Microsoft Streets and Trips w/gps reciever doesn’t suck, and is cheap (comparatively). All you need is either enough battery for the trip, or else a DC power-adapter for the cigarette lighter.
I bought a Garmin StreetPilot c340 about a year ago and love it. It’s probably one of the best purchases I’ve made. In addition to the search by name feature which is neat, it also gives me estimated arrival time and top speed-- it’s quite fun trying to reach a new top speed. I’m still impressed by how it knows if I’m in the express lane or local lane-- they’re only like 10’ apart… or if that it knows to yell at me if I take the upper level of the Verrazano Bridge instead of the lower level-- damn you Garmin “Jill” you’re the one that suggested this $9 bridge at least let me choose if I want to be on the upper or lower level.
But any way, here are a couple tips to keep in mind… My Garmin has locked up a couple times at really horrible times, so make sure you know where the reset button is (I have to pop the faceplate off). Also, I found it’s a good idea to keep one eye on the map while I’m driving rather than rely on the voice navigation, because sometime it tells you a little too late-- so I end up counting down the side-streets to the turn I have to make. It’s also very picky about certain address, for example, if the address I want to go to is on Rt. 9, I have to enter it as US 9 instead of Rt. or Route.
Mrs. R just ordered a Garmin Nuvi 350 from Amazon. Many thanks to everyone who responded to this thread. 
I have the first-generation Garmin Nuvi (all of a year old now) and really like having it when I drive, even if I know the way (it’ll tell me how long it’ll take to get somewhere). It does have the ability to input latitude/longitude for geocaching, and is certainly small enough to use for that (which I have done), but it’s primarily a highway-use system.
For more opinions of GPS devices, check out the forums at www.gpspassion.com - there’s a Nuvi specific forum there.