As a college student in my late 30s, I need to hang on to whatever shreds of dignity I can manage, so I save the nylon backpack for hiking. Instead I tote my gear in a Saddleback Leather messenger bag. Not only is it darn near indestructible, but it looks good whether I'm in jeans and a t-shirt or a jacket and tie.
Inside I've got whatever textbook I'll need for the day plus a book of manuscript paper and a folder of sheet music (I'm studying music education). I also carry a few Uniball Jetstream pens and Bic mechanical pencils as well as a pocket notebook.
For a computer I use Nexus 7 tablet and a Bluetooth keyboard, which, in addition to my email and word processing needs has a handful of musician-specific apps, including a metronome, multitrack recorder, chromatic tuner and an ear-training program. I keep spare cables, adapters and whatnot in a small pencil case so they don't get tangled in the larger bag. The over-the-ear headphones are a requirement for a couple of my classes, but they also make it easier to hear music while working in some of the campus' busier common areas.
A multitool, small roll of duct tape, camera and water bottle are always handy, and I keep a pennywhistle in the bag just because it's always fun to have a musical instrument handy, although more often than not I've also got one of my mandolins or guitars with me as well.