R.
ALL the answers below are great!! I would also like to add swimming...a great and easy tool to use. The pressure from the water all around their skin and the fact that they use all of their limbs provides alot of stimulation. Wears them out too! :)
I also purchased a great chair at Ikea that closes and spins in circles. He loves it. Don't remember the name of it, but you will know it when you see it.