We haven't had trouble with depression but very much with boredom. Brain rest is very key in healing.
With my son, we have found that reading out loud to him seems to help. We read his old favorite books from about fourth grade.
We also let him listen to his Ipod hooked up to speaker and on a low volume while doing range of motion exercises. He is now able to play phase ten dice which also helps pass some time. With the dice game he only has to concentrate on one roll at a time.
He is getting closer to being able to walk independently but until then I take him for many walks in his wheelchair around town.
I know that these sound like very boring ideas. They are, but boredom and low activities are needed for healing.
My son had enough credits his senior year before he was injured, so he has graduated. We did have him go to Spanish and German classes for awhile last year, but he didn't feel comfortable being back into school.
He isn't able to focus enough to go to college yet. If your son goes part-time, be sure to pick classes that are not so much lecture based. Lecture/note taking may overload the brain too much.
Hope this helps some.