My sister went to a felting workshop in the Victorian Alps recently, where she worked on a felted jacket, in a class taught by Raewyn Penrose from New Zealand.
But there is a breed of dog, the Bergamasco Sheep Dog, that doesn't need to buy a felted jacket, because their coat is naturally felted. After I saw the amazing picture of this dog in the new Australian magazine, Felt, I had to look around the internet to find out more about the breed.
I've seen dogs with coats that form mats, but never one that is meant to do so. According to the magazine, the Bergamasco has a fine undercoat, with a protective oily coating to water proof the dog, the middle coat is stronger, somewhat like the guard hairs on a goat, and the top coat, the one that naturally falls into felt, is softer and woolier. The top and middle coats weave together to form the felted 'flocks' which are wide and flat, like ... well.... like felt, actually.
Here are some photos.