I'd pack small, healthy snacks. Thing that will last in a backpack (just think what you could do with a cooler or FitNFresh type container with an icepack...):
PB and Banana Sandwich (whole wheat bread, or a low carb whole wheat wrap)
String cheese/cheese sticks and whole wheat, high fiber crackers
Fruits (oranges are particularly thick-skinned, which is good for portability, but other fruits go into a bag easily as well)
Oatmeal packets (most campuses have a coffee bar - get a cup of hot water like you'd use for tea, add to your oatmeal...they even make "Weight Control" oatmeal packets with a bit more protein, which will help you stay full longer).
Definitely do not let the calorie deficit go! Pack things that you can eat quickly and easily, either all together as a "lunch", or separately as mini-meals throughout the day.
If you want to take things that need to be chilled, these containers are awesome and make great lunch-packers...
http://www.freshapproachdietstore.co..._and_fresh.php
http://www.freshapproachdietstore.co..._and_fresh.php
http://www.freshapproachdietstore.co..._and_fresh.php