Here is a list of the most popular small dogs in the U.S. in 2011. The list is in order of most popular to least popular. The Beagle was the most popular small breed in the U.S. in 2011. It's easier to find someone who is breeding one of the popular breeds. And it can be very difficult to find someone breeding the less popular breeds.
Affenpinscher
Australian Terrier
Basenji
Beagle
Bedlington Terrier
Bichon Frise
Border Terrier
Boston Terrier
Cairn Terrier
Cavalier King Charles Spaniel
Cesky Terrier
Dandie Dinmont Terrier
English Cocker Spaniel
English Toy Spaniel
Fox Terrier Smooth
Fox Terrier Toy
Fox Terrier Wire
French Bulldog
Glen of Imaal Terrier
Havanese
Italian Greyhound
Japanese Chin
Lhasa Apso
Lowchen
Maltese
Miniature Bull Terrier
Miniature Pinscher
Norfolk Terrier
Norwich Terrier
Papillon
Pekingese
Petit Basset Griffon Vendeen
Pomeranian
Pug
Puli
Schipperke
Schnauzer Miniature
Scottish Terrier
Sealyham Terrier
Shih Tzu
Silky Terrier
Skye Terrier
Swedish Vallhund
Tibetan Spaniel
Welsh Corgi Cardigan
Welsh Corgi Pembroke
Yorkshire Terrier Yorkie