go to animal planet dot com and do the dog breed selector program. It will give you a starting place at least.
But I have to really agree with Bug. Her advice mirrors my sister who is a dog groomer, and a good friend of mine who is a vet tech. The BEST way to find a dog at a shelter is to go meet the ones who fit some basic criteria (size, temperment, etc).
Another idea is to go talk to some groomers and vet techs. They can give you some information about breeds you might be interested in.
Training is a HUGE key with EVERY dog breed. ANY dog can bite and be a mean viscious dog if not properly trained and socialized. Just like ANY dog can be a great family dog with proper training and socialization.
Realize some dogs have longer "puppy" phases (labs for one), some can be kinda stupid (beagles), some have more stubborn personalities, some are working breeds and NEED lots of exercise (dalmations NEED to be RUN not walked RUN 3 miles a day), some are super super intelligent and NEED interaction (labs, shepards) and REALLY good training, some have a LOT of bulk to them, Some require a LOT of grooming, etc and so on. Knowing which breeds have tendencies toward what is a good step. Which is where the dog breed selector on animal planet comes in. It asks 10 questions about your family and lifestyle and amount of effort you want to put into a dog.
Also I'd suggest taping (I think I just dated myself with that statement LOL) the show dogs 101 on Animal Planet. Each show goes through about 4 breeds (maybe 5) and you get a really great introduction to breeds.
Be aware though that LOTS (in fact I'd say a good majority of dogs in shelters) are mixed breeds and may or may not have the best of both breeds in them.
I hope this helps some and good luck with your decision :)
ETA: there is no such thing as a hypoallergenic dog. Why? because people aren't allergic to the HAIR/FUR, they are allergic to the dander which is the skin and skin oils. Some people react to some and not others.