I would also be interested in a comprehensive listing of locations that allow pets, so I can avoid them when possible.

Two negative experiences that I have had:
1) The Ocala, FL Hilton, right in the middle of "Horse Country". When even the elevators smell of wet dog, don't expect much from the rooms.

2) Not a Hilton, but stayed at a Sheraton in Tampa. Was laying in bed reading, had a flea jump on me, then saw two or three more when I looked over the bed. Examined the room, and the bathroom had hundreds of dead fleas in an oily goo around the edges of the room. Packed up my stuff and went to the office, they told me they had hosted a horse show recently and most of the attendees had dogs.
They had sprayed the rooms for fleas, but some of them were just overwhelmingly infested. Luckily, the room they reassigned me to did not have fleas.