I haven't read all the posts, but (cooking for two here) some of our favorites are:
Sloppy Joe's - 1 lb. hamburger meat (less than $.50 on sale) + sloppy joe mix (in a can) (about $.75) + buns (maybe $2?) = cheap, easy dinner!
Appetizer dinner - I usually make this with what we have on hand - I buy 3 lb. bags of pepperoni slices from Sam's (they last for months!) - take crescent rolls (about $1 for 8), roll them out into the triangles, then add 5 pepperoni slices and half of a string cheese stick (bought in bulk - about 48 sticks for $8-9), then roll it up, sprinkle garlic powder on it, and then cook according to the crescent roll instructions. Warm up some pizza sauce (you can make your own with spices - on hand - and tomato sauce - about $.50!) and serve. I also will pop some popcorn (olive oil - about $7 for a bottle that lasts for months, so I usually have this on hand - and kernels - maybe $4, and this also lasts for months = healthy and filling) and will serve cheese (block cheese - a lb. for $4 at Sam's) and crackers (a box of 4 stacks of Ritz for $5 at Sam's). Enough to feed several!
Spaghetti or lasagna roll-ups - this is a big one in our house! We buy the big 10 can of spaghetti sauce from Sam's (about $7 - lasts for about 3-4 meals) and then add to it (spices, onion, minced fresh garlic, and meat) when I make spaghetti. If you want to mix it up with lasagna stuff, just make the spaghetti sauce (using 1 lb of ground meat - sausage, beef, or turkey - the same way you would with the spaghetti sauce, just make it a little thicker), cook some lasagna noodles, and "stuff and roll" the sauce into the noodles. You have a layer of straight sauce (no additions, straight from the can), put the now-rolled lasagna noodles down, and then top it with more sauce and some shredded cheese - cook in the oven for about 15 minutes and then you have a cross between spaghetti and lasagna.
Fish and rice - tilapia (I got 3 bags for the cost of 1!), crusted in parmesan cheese (that we already had) and baked, and made rice (got a 25 lb bag for less than $15 from Sam's!).
Beef Stew - 1 lb of stew beef (I only get this when it's on sale - actually, I usually just get straight steak when it's on sale and then cut it up myself - then I can cut strips for fajitas or cubes for stew (or both!), green beans, carrots, onion, celery, beef broth, and spices - I usually have all of this on hand! Just let it stew in the crockpot all day and come home to dinner ready!
Burritos - 1 lb ground meat, rice from Sam's (see above) with spices - crushed red pepper flakes and cilantro, taco seasoning, and spinach, cut tomatoes, cheese, and tortillas (we usually have all of this on hand).
Baked Potatoes - baked russet potatoes with chili (from a can), cheese, and bacon bits on top