At my school's union they had healthy choices that were pretty low cost- maybe your college offers the same thing. You could get packages of fruit or veggies anywhere from 75 cents. I think they tried to offer healthy choices at a fairly inexpensive cost to encourage students to eat that over, say, Pizza Hut.

If that's not an option raw fruits and veggies transport well. There's always dried fruit, too, or trail mix, granola bars, and one of my favorite "on the go" snacks is popcorn. Even pre-popped it is still low-calorie and high-fiber. If you bring a small container of peanut butter you can dip your fruits & veggies too, or if you want something really tasty, one of my favorite treats is pretzels dipped in a little Nutella.