for breakfasts we usually get cereal (little boxes or big box and plastic bowls), pop tarts, granola bars, juice boxes, bananas, fig newtons...
if you plan to pack or eat lunches in your room a loaf of bread, small jar of pb, small jar of jelly... or if you are getting a fridge, cold cuts...
if you plan to spend evening snack time in your room, pretzels, chips, cookies, soda, etc... there is a microwave in most food courts so if micro-popcorn is your thing, buy that too! also, the shelf stable cheese is good w/crackers...
we also like apples, grapes, other easy to eat fruit (ie does not need to be peeled)
you may also want to pick up some ziplock bags or garbage bags for wet stuff... any otc meds you may have forgotten... diapers if you have a little one and don't want to pack a week's worth...
hth... enjoy!