Kids that age .... Gift Cards or pre-paid credit cards. Most collages have their own cards too. Like UT Arlington has Maverick Money cards. They can be used on campus and even some restaurants and stores off campus.
If you want to give more than just a card, how about setting them up with a "medicine cabinet". Buy a large tupperware container and fill it with tylenol, pepto bismal, benadril, ny-quil, band-aids, neosporin, sun screen, etc. All the stuff kids wouldn't think of buying until the middle of the night when they need it. My grandmother gave me this and a sewing kit as a wedding present and it really came in handy. (I do the same thing for baby showers. Buy the diaper bag they register for and fill it with infant tyleonl, diaper rash cream, etc.)
Hope this helps, and congrats to your grads!