I try to do things like get a large package of chicken and freeze individual portions, make a large pot of quinoa and use it for several different purposes through the week (ie: for breakfast one day, in a salad another, as a main course w/ protein on another night).
I also will plan several meals from one roast. Example: make a traditional pot roast in the crockpot one night. Use the leftover for shredded beef tacos another night, then you could always make enchiladas with any leftovers, eat one half, freeze the other, etc.