I am looking for the most cost effective solution to ship a car from
Palo Alto to the Reno, NV airport.  The car is a rental car that I
need to return to an outlet at the Reno airport.

You should check out uship (http://www.uship.com). On uship, you can
list for free that you would like your car shipped. Drivers will bid
for the lowest price and you can save quite a bit of money. I recently
used uship to move from California to Texas. I had my whole 2 bedroom
apartment and my car shipped for $2500. We got other quotes for over
$4000 just for the apartment's contents. Hope this helps.