Engineering college student here... I've ground through a week without sleep.... after a while you pick up the ability to get a really deep rest while sorta conscious... Unfortunately your productivity just drops like a rock. Youar abiliity to tell you can't do anything goes away too, so it's almost a vicious cycle.
What's really fun is when the hallucinations pop in.. around 48 hours I get auditory hallucinations (footsteps behind me, people calling my name, clicking noises)... shortly after I see light patterns... and around 72 hours I'm seeing clowns, turkey legs and teddy bears. Thankfully, it's too insane, so I can pick out what's fake.
If you *need* to drive while sleep deprived, bring lots of caffeine, and... an ice pack. Cold seems to keep me up really well... nothing keeps me on target like a frosty crotch (sounds nuts, but it works). I usually also have a rap CD, which keeps me awake on account of anger. If you have someone in the car with you, try not to go on about normal stuff; you'll nod off... try to argue over something; anger and high level thinking keep most people going pretty well.
That's pretty much all I can think of for now.. it is 5:14 and I'm on summer break. Old habits die hard.