There have been several threads about this around here so do a search and I bet you can get even more ideas. I love these threads though so the more the better. I am always looking for cheap meals.
If you are really serious about your budget and you have an Aldi near you, that is the way to go I tell you! They are cheap! For example:
Meatball subs
1 lb bag of meatballs $1.69
Lg jar of spaghetti sauce .99c (and it's way better than Rago or Prego IMO)
Hotdog buns, whole wheat .89
Had enough meatballs and sauce leftover for spaghetti two nights later, so add in an 89c box of pasta nad that is two meals for less than $5 total. Well, no, not quite, we also had a tube of 25c biscuits with the pasta and salad both nights, but the bag of salad for both meals was less than $2
My family loves chicken and pasta with white sauce. I use about half a box of pasta, two chicken breasts and the basic white sauce recipe from the Better Homes and Gardens cookbook. I then throw in whatever kind of frozen vegies I have and if I bought them at Aldi that is .89c. (The white sauce recipe if you don't have one is 1 T butter, 1T flour, salt and pepper. Melt the butter over medium heat and stir in the flour and seasonings. Add 3/4 cup milk all at once and whisk. Let it come to a boil then reduce heat and stir it (a lot) until it thickens.)
We also do a lot of chilli and then a couple of days later have chilli mac. My kids don't particularly like the chilli, but they eat the salad and corn bread served with it. (Homemade cornbread is just as easy as making muffins) They all love the chilli mac which for some reason I always serve with cooked broccoli and oragne slices for the side dishes.
Sloppy joes and quick and easy and pretty inexpensive. I use hotdog buns for the kids as it is not quite so "sloppy" then.
ETA: Here, I found one of those threads for you. It's seven pages and has some good stuff
http://www.disboards.com/showthread.php?t=916535&highlight=cheap+meals