There used to be more, but quite a few of them are gone now. We loved the little one in Toon Town and especially the really fun Pooh one, both at Magic Kingdom and both gone now. And, my son was crazy for the Honey I Shrunk the Kids playground. Sad to see it go.

The Boneyard in Dinoland is amazing. Tons of fun. And, as you mentioned, the one on Tom Sawyer's Island is fun. Also, there is a very small one, designed for toddlers, near the exit to Splash Mountain. Those are really the only permanent ones left that I can think of, although the ones they put up for the Flower and Garden Festival at Epcot are cool. There are several water play fountains, like the one mentioned above in Fantasyland and a few in Epcot. Also one at Disney Springs...at least I think that one is still there. And all of the resorts have playgrounds, of course. We think the one at Coronado Springs is particularly neat.