I would never, ever let a car, keys or title/MSO leave my posession until I had all of the money. Some sellers may be less paranoid.
As Tom mentioned banks are good at this type of thing. You give the title to your bank and they talk to the sellers bank. The sellers bank wires the money and your bank overnights the title to the sellers bank. Then you load the car on the transport and you are done.
Alternatively, some of the shipping companies will work with the buyer. He can send them a certified check and the driver will deliver it to you when he comes to pick up the car. Do this on a weekday so you can take the check to your bank and have them call the issuing bank to verify that the check is good before the guy gets the car loaded. There are reportedly a lot of counterfeit cashiers / certified checks going around for big-ticket purchases lately so the verification is important.
You can also use an escrow company, but I think either of the above methods are sufficient and they don't cost anything extra or delay your receipt of the money.
[This message has been edited by Lud (edited 12 June 2002).]