When you look in the phone book or on the Internet for auto shipment or auto transporters, you may find some places advertising "five free quotes" or "auto shipping brokerage." These companies don't ship the vehicles themselves -- instead, they act as clearinghouses for the companies that actually do the trucking to transport auto. Working with a broker may help you get a better price or find a company you wouldn't otherwise know about.
On the other hand, many people prefer to work with a shipper, feeling that they want to be able to personally contact those responsible for their vehicles and make arrangements directly. Both approaches have their advantages and disadvantages. Some companies offer both services, so be sure you know which sort of company you're dealing with and what exactly is included in the service.