Kelley Blue Book
(new & used car pricing)
http://www.kbb.com

N.A.D.A. Guides
(new & used cars, boats, etc.)
http://www.nadaguides.com/

Buying a Safer Car: New Car Assessment Program
http://www.safercar.gov/

Car & Driver
http://www.caranddriver.com/

Cars and Other Vehicles (Digital Librarian)
http://www.digital-librarian.com/cars.html