In fact, there is a long list of DNA companies in the business of helping customers find their ancestry. I cannot think of any one that I would call "the best." However, the International Society of Genetic Genealogy, or ISOGG, does maintain a long list of companies in the business and even lists the specialties of each company. You can find that list at http://www.isogg.org/wiki/List_of_DNA_testing_companies.
Several companies specialize in deep ancestry or in health-related issues or in paternity cases. You will need to determine what kind of DNA tests you want to narrow the search. The ISOGG list includes links to the web sites of each company listed.
You can find a lot more information about genealogy DNA at the ISOGG at http://www.isogg.org/.