kitchen sink is by far the biggest. i have an old flak pack 2.0 which is a good size for me, i use it as a carry on and it holds a few days of clothes. great to hold my 13" mbp, and it carrys my books for school, rarely.
If it's just for college or commuting, then I can heartily recommend the BugEye. It's what I use when I cycle to work. Not too big or too small, but still quite a few pockets etc.
If you can find one I'd recommend the AP Pack. It's what I use for the commute. It fits in a 17" Laptop with plenty of room for text books and what not.