There are multiple clubs that offer dog sports from conformation to tracking; the following are some of the most popular.
The American Kennel Club is open to mixed breeds, as well as purebreds, offers multiple sport events, including agility, conformation, coonhound events, earthdog tests, field trials, herding trials and tests, hunting tests, obedience trials, lure coursing tests and trials, rally trials, and tracking events.
The Australian Shepherd Club of America offers agility, conformation, junior handlers, obedience, stockdog and tracking programs for purebreds as well as mixed breeds.
Canine Performance Events offers 5 levels of titling classes in agility (from Beginners to Championship). Membership is open to all purebred and mixed-breed dogs 15 months or older. Veteran dogs 6 years or older may compete at lower jump heights; standard classes and many game classes are offered; Junior and Physically Challenged Handlers are welcomed.
The North American Dog Agility Council provides agility trials for all breeds of dogs, including mixed breeds, with separate divisions for Veterans and Junior Handlers. In addition to standard agiliity and jumpers, a variety of games such as Chances, Hoopers, Tunnelers, Weavers and Touch 'n Go is offered.
The United Kennel Club offers events for agility, conformation, dock jumping, dog sports, hunting programs, obedience, terrier racing, and weight pulls for America and 25 foreign countries.
The United States Dog Agility Association conducts agility trials for more than 200 different breeds of dogs, including mixed breeds.
Many events can be found at trial secretary, superintendent or event-listing websites such as these:
Agility Events (any venue in any state)