These are terms used for a multitude of things.
Registries:
These are for the papertrail bookkeeping of pedigrees and individual dogs. There are many throughout the world but I will include links here to the ones most commonly referred to...
Continental Kennel Club (note: this is not a reputable organization, so I am not even including a link!)
APRI - America's Pet Registry Inc. (note: this is not a reputable organization, so I am not even including a link!)
Venues:
These are a subset of Registries. They are "places" where you can focus on doing something specific with your dog.
Agility Venues = most common are American Kennel Club (AKC), United Kennel Club (UKC), Canine Performance Events (CPE), North American Dog Agility Council (NADAC), Australian Shepherd Club of America (ASCA), United States Dog Agility Association (USDAA), Teacup Dogs Agility Association (TDAA)
Obedience (and Rally) Venues = American Kennel Club (AKC), United Kennel Club (UKC), Canadian Kennel Club (CKC), Canine Work and Games (C-wags)
Nosework = mainly National Association of Canine Scent Work (NACSW), Ramsey (UKC uses this form)
Therapy Visits = Therapy Dogs International (TDI), Pet Partners (formerly Delta Society)
Clubs:
These clubs can be breed-specific or all-breed. They can be about general training, showing in conformation "dog shows" or performance events.
These types of clubs can be found anywhere, they may focus on a city, county, state, region, or national area. Clubs are a great resource for finding trainers, breeders, veterinarians, and friends!
Grand Rapids Kennel Club
Grand Rapids Agility Club
Ingham County Kennel Club
Capitol City Canine Club (4Cs)
Obedience Training Club of Greater Lansing
Companion Dog Training Club of Flint
Ann Arbor Dog Training Club
Ann Arbor Kennel Club
Kalamazoo Dog Training Club
Michigan Association for Purebred Dogs