Sandwiches, wraps, salads, whole raw fruits, chopped veggies, dried fruits, frozen gogurt, yogurt, granola bars, trail mix, nuts, low-fat cheese sticks, chocolate soy milk, chicken tenders, steamed veggies, Carnation instant breakfast, TONS of water. Those things pretty much kept me alive when I was on campus all day. I would figure out my calories the night before and have everything planned out that I would eat the next day. I'd throw it all in my bad and throughout the day, whenever I was hungry or had time, I'd eat something out of my bag. It wasn't mindless snacking, since I had already portioned out what I would eat that day, but I didn't have to be sitting down and counting calories in my head and eating a full meal.
I worked out first thing of a morning most days then drank a cup of chocolate soy milk mixed with the carnation powder. That and a banana or a banana nut muffin would last me for hours. If I brought yogurt or cheese sticks (string cheese), those would be eaten earliest in the morning when I was hungry so they didn't become warm. Grilled/baked/broiled chicken tenders and steamed veggies were usually my "lunches" as I enjoy the chicken and the veggies both cold. If I had a string cheese, I would sometimes save it until lunch to have a more rounded meal. Salads (with dressing in a small container) and wraps were quick, portable lunches as well. Fruits, nuts, and other things that were shelf stable could be saved to be eaten in the afternoons or on the bus coming home in the evenings before supper.
Invest in some throw away tupperware (not the brand name stuff though) containers that are various sizes and shapes. Gladware and ziploc both make great sizes and shapes. Use these to pack lunches and snacks in as your food won't get crushed or smushed at the bottom of your bag. If you plan it out well, you can fit half a pita and plenty of baby carrots and cherry tomatoes all into one flat, square container which would be a great lunch.
Whew, I'll stop now. I know how frustrating it is "living" on campus through college, but I'm here to say that it CAN be done. You just have to have a little more flexibility and planning and you can do it! If you want any more advice, let me know! (: