I steal milk, yogurt, cottage cheese, and sliced meats from the dining hall.
Mixed nuts are great for snacks. Even if you don't have a job, you can get a big tub of nuts to snack on (hah) for about 10 dollars.
Sometimes I make shakes out of 4 cups of skim milk, 2 cups of plain low-fat kefir, a banana, a packet of instant oatmeal, and two scoops of protein powder. It's gross, but its around 750 calories, with about 70g of protein, and takes 5 minutes and a blender to make.
You can use cottage cheese and peanut butter instead of kefir and oatmeal if you want less carbs and more fat.
Also oatmeal cooked in a microwave mixed with chocolate protein powder and peanut butter.
You can get most of the ingredients for these from your dining hall I think. The protein powder is obviously more expensive, but, as a complete bum, I've started a protein fund: I collect beer cans and water bottles and turn them in at the grocery store for store credit. There are usually garbage cans full of beer most Sundays.
I have no dignity.