One of the biggest complaints people have about taking Amtrak is that they don't have their car when they get where they're going (that and the delays/long trips). Since the 1970's there's been a solution in the form of the Auto Train, which allows passengers to take their cars with them. The train only operates from near Washington, D.C. (Lorton, VA) to near Orlando (Sanford, FL), making it popular amongst those headed to Disney World.
The service started out as a private venture in the 1970's but collapsed in 1981 and was rescued by Amtrak two years later. Typically, the Auto Train operates with two diesel locomotives, five sleeper cars, four diners/lounges, five coaches and a number of the autoracks that carry the cars (you can see the loading platform here). This creates a train sometimes longer than a half-mile. The total trip takes somewhere around 18 hours and costs $224 on top of the cost of the ticket.
In 2006, the train was the highest grossing single train with nearly $50,000,000 in ticket revenue, just shy of the $62,000,000 it costs to operate. That may sound bad, but that's actually fantastic for an Amtrak route. Has anyone ridden this beast? [Source Wikipedia]