I use the Garmin iQue 3600. It's a combo GPS/PDA, so you can use it for
many different things. It's a bit high in the dollar department, but
worth every cent.

I recently bought Garmin's Outdoor Navigator software for $20.00. You
can down load any or all of their nav charts that run on it FREE. I've
downloaded all of the nav charts, but none of their topo charts. The
Outdoor Navigator program only holds 200 charts, so a 1GB (or higher)
SD Memeory Card leaves a lot of extra space for phone numbers and other
info you want to keep track of.

The iQue 3600 may be high priced, but with a $20 nav program and free
charts? Think about it.

If you check eBay you can sometimes get really good deal on the iQue.
You can also find gear to run 12vdc and computer connection it it
doesn't come with the eBay iQue.

Good luck and happy navigating.