Small adaptable, curious dogs make great traveling companions. Small terriers and toys such as Miniature Schnauzers, Poodles, and Pugs make excellent globe-trotters. Larger dogs however, prefer to guard the house and give you a big welcome when you return. But there are always exceptions in both cases due to their personalities.
All dogs should be car-trained as puppies, since this is the most common form of travel for them. If you are dealing with an adult dog who is unaccustomed or afraid of car travel, you may have to make a regular training project out of it. Start out with short drives and graduate to longer trips over time.
The best way for your dog to travel with you in your car is in a pet carrier. An unsecured pet can distract you while driving or interfere with the operation of the vehicle. Too many unsecured pets have jumped from a moving vehicle to be fatally injured, when a carrier or tether could have saved them. Car seats and containment seats are now available and can be secured with your current seat belts, and some form of restraint is being considered mandatory by many states and municipalities around the country.
World Trade Center, April 15 to 18!