I am new to Geocaching ,( only found a few) , I have a Garmin Gps72 which is a very basic unit, but it has worked well the times that I have used it. I use Delorme street altas on a laptop for my maps. the 72 will connect to pc via a serial port and track on map. I just wedge the gps between the dash and windshield for use in veh.
If you already have a laptop, its all you need. The 72 has no maps, but it only cost $160 almost anywhere (even Walmart) . You can make your own interface cables by getting the connectors at pfranc.com. the garmin uses a standard rs232 interface so the interface cables are are just wires. I used old mouse cables for the wires. I had db9 female connector, but you can get db9 conn and cig lighter plugs from radio shack.
I understand the gps76 has basemaps and ext antenna connections, but more money. .check these out if you want a low end gps. I am very satisfied with the quality of Garmin.
I have a friend Who is a Supervisor wth Florida Fish and Game They use the 72 for fixes when writing citations.
I hope this was of some help.