I completely agree with Joe, and cannot stress enough that this is NOT the right way to get a service dog. I know and understand that it is by far the fastest and cheapest way to get your pet dog to be allowed to go places with you, but it is NOT best for your dog, you, or other service dogs.
Assistance Dogs International (ADI) is an international coalition of non-profit organizations which work with all kinds of assistance dogs. ADI has put standards in place to help determine which dogs (and organizations to train them) are safe to have out in public. Many other countries require proof that your service dog has met these standards, however here in the US we do not have such a law- and websites like the one you found- know, and take advantage of that.
I have a professional background in training service dogs, and I cannot express enough that not all super-loving, well-behaved dogs are cut out to be service dogs. Most ADI programs specifically breed service dogs, which begin their training the day they are born. These are dogs which have been exposed to new sights/sounds/places since they were born- Yet, on average, only 50% of these dogs will actually become working service dogs. This is because at some point during the 2 year training process, professional trainers have noticed signs of the dogs becoming stressed or unhappy with the pressures of service dog life.
An ADI program has you, and your dog's best interest at the heart of what they do so they will only certify a dog they are confident will handle life out in public well. ADI programs will also take the time to teach you how to use your dog most effectively and how to handle issues that arise. Additionally, most ADI programs do regular retests, so if your dog begins to develop an issue years into it's career then a professional can spot it quickly (before it becomes a major problem) and help you resolve it.
Almost all ADI organizations have an owner-trained program, so if you need a service dog (i.e., you have a disability which drastically limits your daily functioning) and you feel that your pet dog is up to the job, then I urge you to find an ADI accredited organization to work with. Their program search is at this link:
http://www.assistancedogsinternational.org/members/programs-search/
If you do not genuinely need a service dog, but want to find a way a way for your dog to help people, then a therapy dog certification is a great idea. Or, if you want to spend more time with your dog out in public then find local stores which allow pets (most hardware stores and pet stores are good places to start). Agility or rally programs are also fun ways to spend time working and strengthening your bond with your dog.
I apologize for the somewhat outrageous length of this post- this is a topic near, and dear, to my heart and I hate to see people damaging their relationship with their dog (and their dog's quality of life) because they took the easy way out and just bought a "service dog" harness or tag off the internet.