Chris has a couple of great posts on Presidential vehicles

Above: LBJ driving his Fiat Jolly

Above: The carriage Lincoln was riding in to the theater... the carriage was bought by the Studebaker brothers, along with the carriages of Grant, Harrison, and McKinley. They are all in the Studebaker museum

For a set of great posts about the Presidential limos, carriages and personal cars: http://chrisoncars.com/