Hello HydroJim, you've gotten some good ideas here, and I will add a few more. First, I suggest using your meal plan meals for dinners because they are the most expensive to make, so that's the best bang for your buck. If you are allowed to take pieces of fruit out of your dorm cafeteria with you, by all means do so up to the limit you are allowed (bananas, apples, oranges are often available). They will come in handy for breakfasts and snacks.
Okay, so now you're looking at breakfasts, lunches, and some dinners. Breakfast is super-easy. We like to keep breakfast costs under a dollar a day, which generally means eggs, oatmeal, or cold cereal. Buy a cold cereal you like in a huge bag and buy an off-brand rather than a name brand. A gallon of milk and you're good to go -- but keep an eye on portion size because it's easy to over-eat when you buy in large quantities, and then you erase your savings.
For egg-based breakfasts, visit the website incredibleegg.org and search on "microwave." You'll see about 10 pages of results. You don't have to eat eggs the same way over and over!
For oatmeal:
http://www.bhg.com/recipes/how-to/cooking-basics/how-to-cook-oatmeal/. Add fresh fruit, sugar, raisins, etc. to vary endlessly.
Here's a kind of pancake-in-a-mug:
http://www.budgetbytes.com/2013/02/blueberry-mug-muffin/ . You could use any fruit you have handy -- or none at all.
Yogurts also work well for breakfasts or lunch. Buy what's cheapest.
On to lunch. The obvious options are sandwiches and salads, and rice bowls are a nice quick alternative. I mean GOOD sandwiches. Buy yourself some good bread -- around here we prefer a take-and-bake baguette. We don't bake it though -- we find it's sturdy enough already and a little easier to eat without a harder crust. One baguette divided into fourths and then split lengthwise like a hotdog bun is perfect for me -- my son prefers them split into thirds, which fits his appetite but is slightly more expensive. Use a good mustard or other condiment sparingly (salad dressing works great also). Buy a good cheese that you love and slice it paper thin -- a little can go a long way with flavor and is worth the money in my opinion. Buy yourself some lunch meat and ration it sensibly -- I find that three slices of deli meat is a good amount per sandwich, so I can get quite a few sandwiches out of a package of lunch meat. If bell peppers are cheap I like to put in some thin slices of that. Marinated peppers from a jar will do also (I just buy the cheapest brand). A few leaves from a bag of salad greens and you have a sandwich that is actually worth looking forward to eating, for less than you'd spend on fast food. I know I am belaboring the obvious, but my point is there is a huge difference between a nasty sandwich on wonderbread, which will make you feel deprived, and the kind of sandwich that makes your day and that others envy. Experiment and figure out what ingredients will make a sandwich that you actually love. Other options besides a traditional sandwich are pita bread and tortillas for wraps, either of which can hold practically anything.
Salads I assume are self-explanatory, but you will discover that fresh produce prices vary dramatically by season.
Rice bowls are great in cold weather. In a bowl, combine cooked rice (more on that in a second), some cooked beans (from a can is fine -- black beans, kidney beans, pinto beans all great), some frozen corn (no need to thaw), a few spoonfuls of salsa (whatever is cheap is fine -- we like Pace), and a small amount of shredded cheese -- cheddar is fine, pepper jack is great, whatever. Stir to combine and microwave until the cheese melts. The whole thing takes about 2 minutes to make and is unbelievably filling,
You can cook rice in the microwave by the way:
http://www.food.com/recipe/perfect-easy-microwave-rice-195326. Cook a larger amount and then you've already got it on hand. It keeps for a few days in the fridge or portion it into Ziploc bags and freeze it for weeks.
I'll post about dinner ideas in a bit -- this post is getting pretty long!