Baked Beanie Weenies -- We buy cans of pork and beans whenever they are on sale (often on sale for .50/can), and a large pack of hot dogs (Gwaltney packages them as many as 24 to a pack for less than $5 for the pork and chicken kind). I combine several cans of pork and beans in a casserole dish, usually allowing one can per family member, and I add ketchup, mustard, BBO sauce, and brown sugar to make the baked beans, and then I cut up a couple of hot dogs per person, stir them in, and bake at 350 for about 40 minutes or so. For our family of four, that's four cans of p-n-b, and eight hot dogs.
Pancakes/Waffles -- Cheap for the most part because it involves mostly staples like flour, oil, sugar, eggs, and milk that everyone keeps on hand. The only real extra expense is syrup, and maybe bacon or sausage if you wanna get fancy.
Soup -- Our grocery store right now has 10 cans of chicken noodle soup and tomato soup for $6. Not the store brand, either, but Campbell's. They've got store brand crackers on sale this week too. Always keep soup on hand, and "cream of" soup for gravies and crock pots, and chicken/beef broth (which are good in soup instead of water).
Oyster stew -- Two cans of condensed milk, two cans of water, one stick of butter, and two cans of oysters. Heat on medium or medium low until hot, eat with or without crackers, and stir in a small amount of ketchup for a bit of extra flavor, and some pepper and hot sauce for some zing. My family always ate it like that, with some gherkin pickles for a bit of sweet. Again, catch the condensed milk on sale (like around Christmas) and the biggest expense we have is the oysters, which are less than $2 per small can. Condensed milk is always good to keep on hand for the times when you run out of "regular" milk.
Boxed mac and cheese -- Again, they often go on sale, and even the store brand is pretty good. I'd like to try condensed milk in this instead of regular milk sometime, but I haven't yet.
Canned veggies often go on sale at our grocery store, so those are good to stock up on.
"Oir is leatsa an rioghachd, agus an cumhachd, agus a gloir, gu siorraidh, Amen." ("For Thine is the kingdom, and the power, and the glory, forever, Amen" -- Scots Gaelic)