a lot depends on from and to where so that will help get suggestions for you.
Otherwise, I used JP Logistics -
www.jplogistics.net to ship a car enclosed from CA to PA and they were good.
A common one I see often and hear decent things about is Intercity Lines
www.intercitylines.com
Never used but have heard FexEx Custom Critical is decent too customcritical.fedex.com/auto
Best suggestion is to find the carriers who commonly run from/to where you want the car shipped and get their quotes. Then post here to get specific feedback. Most haulers will tell you they'll gladly ship from A to B but you want the ones who do it often to get the best rate, time frame and service.
Good luck