All that old US military stuff is fine and good, and would serve your purposes - but they lack a bit in the class department. Personally, I use an old Swiss rucksack as my bookbag for college, and it does quite a job while looking rather nice as well. It looks like this, except this guy's gone and put some funky patch on it and the bag in the picture is obviously totally empty.
Once you put some stuff in it, it looks rather nice. None of the pictures I could find quite capture the beauty of the bag, but you get the idea.
Everything on the bag is practically bomb-proof. The stitching is well done and the leather is quality. The bag actually does have a light internal frame, and has this big sort of inner lining that can be used to extend the bag's carrying capacity. Overall, it's the best damn bag I could find for my tastes and purposes, and being Swiss made is a definite plus.
I got mine for $50 at a place called Out Your Backdoor (suggestive, innit?) but your mileage may vary. They're a little bit difficult to find - and be sure you call who you buy from to make sure they're in stock. I waited weeks for a certain surplus store to send one, called them and found out it was backordered. :jerkit:
Jerkarounds aside, if you can find it at a reputable dealer for a reasonable price, I would highly reccomend the rucksack. It's probably not suitable for long trips, but it's damn skippy for toting around the campus. Just search for "Swiss rucksack" and you're likely to find a few hits. Good luck.