You're very welcome. Hopefully there are some new units with USB connectors; last time I checked, everything was through a serial port.
Otherwise, I highly recommend the GPSMAP76S, the unit I use. If I were buying today I'd go for the GPAMAP76SC (yeah, the color screen is a bunch extra and probably not worth the extra cost, but it would be a business expense).
A simple lightweight unit primarily for backpacking, can't beat the Garmin eTrex Legend.
For under $100, the yellow eTrex Basic is perfectly capable of everything you have in mind.
Wonder if there's a PCMCIA card with a serial port replicator?
One other tidbit, many of the GPS units have a port for an external antenna. In my vehicles I get excellent reception through the moonroof or front window. Some new cars have a metallic windshield coating and you won't get a signal through it. Best bet, a magnetic external antenna on the roof. Also great for mapping hiking trails - toss the GPS in the pack, have the antenna stuck on the pack exterior, and hike away!
Any really tough GPS questions, try asking over at the Geocaching forum. Those people know more about consumer GPS units than anyone on the planet.
Best Wishes,
Bob