The Labrador retriever has been the most popular dog breed in the U.S. since 1991, according to American Kennel Club registration statistics. Rounding out the top five for 2009: German shepherd dog, Yorkshire terrier, golden retriever, and beagle.

Cousin to the bulldog, the medium-size boxer gets its name from its penchant for standing on its hind legs and batting at its opponent or playmate with its front legs—boxing, in other words.

It's all about the nose for dogs. Smell is their most remarkable natural sense, boosted by as many as 220 million olfactory receptors. (In comparison, humans have five to ten million.)

In 1937, deaf and blind author and lecturer Helen Keller became enchanted with Akitas on a visit to Japan and was presented with one as a gift. "If I cried from loneliness for my beloved teacher, he would put his big paw on my knee and press his cool nose against my cheek and lick away the tears," she wrote.

Known as the "barkless dog," the basenji makes a yodelling noise instead. It also cleans itself like a cat and lacks the typical doggy odour.The Basenji is a breed of hunting dog. It was bred from stock that originated in central Africa. Most of the major kennel clubs in the English-speaking world place the breed in the hound group—more specifically, in the sighthound type.