Crossing the Darien Gap – Esmeraldas, Ecuador Travel Blog - Puerto Caldera, Costa Rica to Guayanquil, Ecuador
South American Explorers - Panama City, Panama to Manta, Ecuador
Dave Thompson - Mostly for motorcyclists, but good overview for everyone
Glenn’s South American Oddssy - Panama to Colombia
Project Allende: June 2004 Archives - scroll down to the section labelled “Mind the Gap”
The Silk Route Motorcaravan Network - Panama to Colombia. Kept a great record of the shipping companies they contacted.
Traveling by Car from Detroit to Buenos Aires - Panama to Colombia (Scroll down to section labeled: The Mama of All Border Crossings)
Expedition Calendar - Panama to Venezuela (2005)
Overland in a VW Camper (Westfalia) through Mexico, Central America, South America, and Africa - is also a good compilation of people sharing their own experiences with shipping their car to South America.