There is the Canine Good Citizen test (http://www.akc.org/dog-owners/training/canine-good-citizen/), and the more stringent Community Canine Good Citizen Test (http://www.akc.org/dog-owners/training/akc-community-canine/).

I've used this informally as justification before when renting housing and bringing my dog to work (she's a plain CGC).

I think there's value in having these be more recognized. I especially wish they were by airlines.

Note that this isn't the same thing as the issue with service animals, where credentials are at a totally different standard, and more important than where I can bring my pet.