I gave up cereal a long time ago. It's expensive, it's full of added sugar, and most damning, it's not filling. After eating a bowl of cereal, I'm usually hungry an hour later. Plus, cereal requires me to keep milk around, which I don't usually do. (For recipes which require milk, I generally use powdered milk. I don't have to worry about it going bad, and there's no noticable taste difference.) But I still required a simple, portable, cheap breakfast I could take to work and eat there.
Enter the muffin. I make a batch every week (10-12 muffins), and take them all to work. Two muffins each morning, reheated, is a warm, comforting, very filling breakfast that will take me through till lunch. Note: These are regular-size muffins, made in a standard size muffin pan. Don't picture those 1,000-calorie monstrosities at Starbuck's. Those muffins aren't muffins, those are an excuse to eat half a cake.
Almost anything can be added to the basic recipe. Fresh fruit. Frozen fruit (I'm partial to frozen blueberries.) Overripe bananas, mashed up. Nuts. Raisins. Cranberries. Pumpkin puree. Chocolate chips. A combination of any of the above. Just stir into the batter recipe below. If you have some berries that are going to go bad soon, chop them up and throw them in the freezer. You can retrieve them later to put in these muffins. I've made multi-berry muffins before, with bits of frozen strawberries, raspberries, blueberries, cherries, whatever I had floating around in small amounts in the freezer.
I also like to make jam muffins. Double the recipe below, and fill the muffin cups up halfway with half the batter. Add a big spoonful of jam to each cup, then top with the other half of the batter. If you don't have any fruit available, you always have jam in your fridge.
1 3/4 cups all-purpose flour
1/3 cup sugar
2 teaspoons baking powder
1/4 cup vegetable oil
3/4 cup milk (I usually use powdered milk, reconstituted)
Mix, add whatever you're going to add, and place in a greased muffin tin. Bake at 400 for 20 minutes.
Ingredients in bulk, plus jam (homemade, free, thanks Mom!) or whatever leftover yummies I have available: maybe 10 or 15 cents each? Let's say a quarter, every morning, for breakfast. The calorie count is pretty minimal (you can scale back the sugar further if you want), and these are homemade, so you don't have to worry about preservatives. 30 seconds in the microwave every morning, eat at your desk. Done.
If you have kids, you can make two or three batches at once, of different varieties, and let them pick. A better breakfast than cereal, and while some kids balk at oatmeal, everybody likes muffins.