Dogs have been selectively bred for thousands of years, sometimes by inbreeding dogs from the same ancestral lines, sometimes by mixing dogs from very different lines. The process continues today, resulting in a widening in appearance without speciation, "from the Chihuahua to the Great Dane."
The following list uses a wide interpretation of "breed." Breeds are usually categorized by the functional type from which the breed was developed. The basic types are companion dogs, guard dogs, hunting dogs, herding dogs, and working dogs, although there are many other types and subtypes. Breeds listed here may be traditional breeds with long histories as registered breeds, rare breeds with their own registries, or new breeds that may still be under development.
Though groups like the American Kennel Club make very specific designations about breeds and breed hybrids, there continue to be new breeds and breed variants developed all the time, as well as "up and coming breeds" not officially recognized by kennel clubs and experts. (Many dogs not purchased directly from breeders are also mixed-breeds of some kind, or have less than purebred ancestry.)
For example, a bill currently under consideration in New Jersey would ban breeders from selling dogs outside the state unless the sale was made face-to-face. If you are a breeder in New Jersey and a potential buyer in say, California, is interested in one of your dogs, this buyer would have to come to New Jersey to see and buy the dog. Or the breeder would have to take the dog to California. This is obviously onerous and unnecessary. It also adds a tremendous expense to the cost of the dog. This kind of legislation is proposed in the name of “consumer protection” but it is actually meant to punish and discourage dog breeding.