last year (in response to Bankrate's "eat your leftovers" savings challenge), leftovers have never been a big problem at our house. We just eat them for lunch—or, if there's enough left over, for a second dinner. The only time this ever causes any problems is when we've made a new recipe that neither of us liked very much, such as last month's cucumber salad with yogurt-dill dressing. But even then, Brian can usually manage to dispose of it if he's hungry enough. (Side note: we did try this salad with the lemon-tahini dressing instead, adding some chick peas to give it more substance, and it was better, but still not quite there. Next time, we plan to add more tahini, more garlic, a bit of cumin, and a touch of honey to tone down the brightness of the lemon juice.)
However, I've been given to understand that we're very much in the minority on this point. A 2012 study by the National Resources Defense Council (NRDC) found that the average American household throws away about 25% of all the food it buys, to the tune of $1,365 to $2,275 per year. A 2015 survey by the American Chemistry Council came up with less dramatic, but still significant estimate of $640 worth of food wasted per household per year.
The NRDC notes that food gets wasted for several reasons, including spoilage and misunderstandings about use-by dates, but part of the problem is "over-preparation": cooking a meal that's too big and ending up with "uneaten leftovers." So clearly, finding a way to turn those into eaten leftovers would save most families money, as well as reducing waste.
To that end, I've written a piece for Money Crashers on all the different things you can do with leftovers. Many of these are tricks we use ourselves, such as eating leftovers for lunch, throwing odds and ends into flexible recipes like stir-fry and frittata, and turning bones and vegetable scraps into stock. Others are ideas I've picked up from frugal-living books and websites, including homemade freezer meals, the leftover smorgasbord, and the "perpetual soup container" (throw all your leftover meat and veggies in, and when it gets full, just add water and cross your fingers).
So I can't personally vouch for all the ideas in the article—but I can confirm that they're all ideas that someone out there has tried and found good enough to recommend. With a little luck, you should be able to find at least a few that work for you as well.