We had this AWESOME light table dontated to use from Donorschoose.org. (We are so lucky!) The light table is a sensory activity, perfect for students with sensory integration issues. One of our favorite things to play with on the light table are water beads (another sensory based play material).
Be sure not to waste your money on fancy water beads. I found this 10 pack of water beads on Amazon.com for $1.69! Of course I bought several sets. The process of hydrating the tiny water beads is also an exciting activity for little people.