the Facel Vega I posted about last year http://justacarguy.blogspot.com/2009/03/dean-martin-and-facel-vega.html
Accoding to http://www.dexigner.com/product/news-g12107.html Dean owned one of these 1967 Ferrari 412P on exhibit at the Cincinnati Art Museum.
a 1976 Stutz Blackhawk 
from what I could learn in searching the internet, Dean owned this Ghis L 6.4, a 1967 De Tomaso Mangusta Fantuzzi Targa, a 1966 Ferrari 330 GTC, and a 1972 Cadillac station wagon: http://justacarguy.blogspot.com/2009/03/1972-cadillac-station-wagon-1-of-2-made.html If you loved Dean Martin, and want to check out a really cool laid back blog about him, his movies, some stills, and some video clips, ya gotta go see http://ilovedinomartin.blogspot.com/