Whenever I am in a budget crunch, I tend to make a lot of pasta...pasta with sausages, olive oil and parmesan, pasta with spinach (I cut it into small pieces to make it less offensive to my children...they think it's basil

) cheese and pinenuts (I know they're expensive, but you don't need to use many) or a favorite of mine from some magazine is pasta with asparagus...when it's on sale. Cook the asparagus until tender. Blend it in a food processor with the zest of a lemon and olive oil. Cook the pasta. Toss with the sauce and top with parmesan cheese. Yum. Of course, my children hate that.
I also tend to make homemade macaroni and cheese...pasta, butter, milk, cheddar and monterey jack cheese, and a little Velveeta to make it smooth. If I really want to be a mean mom, I add green vegetables like peas, broccoli or spinach. DD gets very mad.
Then there are always quesadillas. DD will only eat cheese in hers. DS will accept black beans, with no flavorings. I add whatever is available to mine.
And of course, the freezer is your friend. In the colder months, I like to always have a supply of meatballs (you can make them out of ground chicken to save money and cholesterol!...just add a little more flavoring), ravioli, sweet potato burritoes (the recipe is longish, but PM me if you want it), and lasagne.
There are also the built-in leftovers. Roast chicken is great because you can turn the leftovers into a pot-pie, a soup or a sandwich. Pasta and vegetable leftovers can be made into a fritatta. Leftover mashed potatoes make excellent potato pancakes and I love leftover risotto, which I didn't mention previously but is a great money-saving meal, as risotto cakes.
Sorry this was so long...I just love talking about food!