We do a lot of casseroles in our house. It's just me and DH, but I'll often double a recipe. That way, I have lots of leftovers, or even a whole second pan to freeze. I made a double batch of the Moosewood Restaurant's Black Bean Chilaquile last night. Cheap, filling, and that will feed us an assortment of lunches and dinners for a few days (even with DH's appetite!).

Anything in the crockpot is popular too. Chili, stew, roasts....

Veggie omelets are another easy, healthy dinner for those "we didn't plan anything" nights.