My current solution is low-tech, but it works! I seat-belt my Laptop (Compaq Armada 1700) sideways into the passenger seat. Since the PCMCIA slots are on the right hand side of the machine, I use my garage door opener as a spacer to keep the Orinoco card and pig tail connector from touching the seat (prevents wear and tear).
This last weekend I had to travel from Louisville, KY to Erie, PA, and this set up worked real nice. With power from the cigarette lighter and a cassette converter feeding audio into the van's radio, I listened to MP3s and stumbled all the way up.
I may invest in a better solution some day, but for now this solution provides quick setup and easy tear-down.

Bill