Let him use the computer... there are many learning sites. Sorry I forget which ones. But my daughter's Teacher has a list.
Wheel him around in the house, in a stroller... those umbrella strollers.
MUCH easier. If my 7 year old can fit in it, then he can. My daughter had a badly sprained foot with a cast on it, and this is what we did. Stroller. In the house and out. Very helpful.
Also, get him crutches. VERY helpful. Kids CAN use these.
Let him do art work, reading, computer, cooking at a table, play doh, coloring, card games, checkers, "Think Fun" has some great kids games that can be played with only 1 person (barnes & noble carries it and Amazon), puzzles, crafts, movies,
maybe get him a Leapster... its REAL good and educational and both my kids LOVE it.
All the best,