Hi B.,
I just responded to Mikki as well. Basically, here's what I wrote:
For my son's 16th birthday we had a "blowout" music and movie party. We set up Singstar in the living room, and Rock Band in another room. We set up teams to compete on who got the most points. The team thing fell apart, but it turned out even better as everyone got involved in different ways than they would have. We had the usual food -- pizza, munchies, cake -- but a friend loaned me her chocolate fountain. Another hit! I bought champagne flutes at the dollar store and, when we cut the cake, I poured sparkling cider into the champagne flutes. There was music playing and they all danced. Later, some of the kids went home but the majority stayed over and watched movies all night. Everyone agreed it was the best party.
So, find something your son likes to do and try to do it up as much as you can. It doesn't have to cost a lot of money. Do you have friends you can borrow stuff from -- like we did with Rock Band? Is there a vacation house someone owns that you can borrow to take your son and a few friends to for an overnight?
Sometimes it matters most who is there rather than what they do. My daughter (turning 15) is perfectly content with a sleepover with her friends for a birthday party.
They have a blast!
Make whatever you do memorable, whether you do a karaoke contest and video tape it, or take a ton of photos while they are playing charades. You can make an album or other keepsake to help him remember the fun.
One other thought -- cosmic bowling. I don't know what it is about bowling, but I've never met a person who had a bad time at a bowling party. There are some lanes that have something like cosmic or laser bowling, where they turn out the lights and turn up the music.
Have a great time, whatever you do.