American Kennel Club (AKC) http://www.akc.org/
Started in 1884, the AKC is the oldest and probably largest registry of purebred dogs. They provide for registration, pedigrees, performance and conformation titles, education, health and genetic issues and more. Most reputable breeders of recognized breeds register there dogs and puppies with the AKC.

American Cavalier King Charles Spaniel Club, Inc (Am CKCS) http://www.ackcsc.org/
The Am CKCS is the AKC parent club for Cavalier King Charles Spaniels. 

Cavalier King Charles Spaniel Club (CKCSC) http://www.ckcsc.org/
The CKCSC - USA. Inc. is the original registry for Cavalier King Charles Spaniels in the United States. The club was founded in 1954 and currently has over 2000 members.

Cavalier King Charles Spaniel Club of Central Ohio (CKCSCCO) http://www.CKCSCCO.org/   The Cavalier King Charles Spaniel Club of Central Ohio is a new club currently under development. The Club will be working under guidance from the American Cavalier King Charles Spaniel Club and the American Kennel Club with a goal of becoming an AKC licensed club.

Labrador Retriever Club (LRC) http://www.thelabradorclub.com/
The LRC is a nationally based club dedicated to preserving the integrity of the breed. Formed in 1931, the club has a rich history with past and present members and is recognized as the parent club of the breed by the AKC.

National Labrador Retriever Club (NLRC) http://www.labradorretrievers.org/
The NLRC was organized in 1996 with the idea of creating a national club that would preserve and promote the Labrador Retriever.

Orthopedic Foundation for Canines (OFA) http://www.offa.org/
The OFA was founded to collate and disseminate information concerning orthopedic and genetic diseases of animals and to advise, encourage and establish control programs to lower the incidence of orthopedic and genetic diseases.

Canine Eye Registration Foundation (CERF) http://www.vet.purdue.edu/depts/prog/cerf.html
CERF was founded by a group of concerned purebred owners/breeders with a goal of eliminating heritable eye diseases in purebred dogs through registration, research, and education.