I read this cool story in Dog Fancy, about a shelter in Medford, Oregon, that treats the dogs to playtime on equipment used for agility. People can watch the dogs do it, plus it gets them out of the shelter and play, and they can "show off" in front of potential adopters.
Other shelters that do it are the San Francisco SPCA and the Upper Valley Humane Society (Enfield, NH).

I really think this is a great idea. At least the dogs can enjoy the time they have to stay there, plus learn some new stuff and play and have fun.