You could check here:
http://www.apdt.com/
Or google "[City Name Here] Obedience Club" or "Dog Training Club" or any combination. Most cities have a group or two nearby (check major metropolitan areas near you - sometimes they can refer you to a closer, smaller club).
Then I would ask to go watch a class. See what type of training they do and if it meshes with your ideas about how you want to work with your dog. Do people look like they're having fun? Do the dogs? Personally, I work with mainly positive verbal and food reinforcement - so if I saw they did only clicker training (my dog hates clickers) or say, a lot of chain jerking and physical manhandling (I don't believe this is the best way to teach a dog) - then I would say thanks a lot and go elsewhere. That way you don't shell out $80 for a class and find out you and your dog will be miserable

You can also check the akc website and look for obedience shows in your area, they're often sponsored by a club - that could help you find one as well. Good luck!!