Hi,
The topic right below this was a similar question. You should check it out, it has info and I also pics of my dogs.
But anyway UKC allows Pit Bulls in the show, but this is a "all breed" registry. AKC doesn't have any shows for them but does have the counter part American Staffordshire Terrier. You can UKC reg an AST but can't AKC an APBT.
If you are looking for shows that are Pit Bull only you can try ADBA or AADR. These have conformation and weight pull shows as well as fun classes and Jr Handlers.
I just got back from a show a couple days ago and will be heading out to another in less then a week.