Well if your dog appears to be a purebred you can get an ILP/PAL number from the AKC that will allow you to compete in all the companion and field events for that breed. It basicaly means you can do everything except conformation. The only requirements are that your dog is fixed and appears to be a purebred. I belive the UKC allows mixed breeds to compete in thier companion and field events as well, but I'm not as familiar with thier system. There's also mixed breed specific clubs/registries out there, though I'm not sure how often they have events for you to compete at and earn titles.