One of my favorite meals to make from leftovers comes about when I have a bit of beef or chicken. I always keep a jar of stir fry sauce (sweet and sour, hoisin, terikyaki) on hand, and it's delicious to dice some of the meat and fry it up with some onions and a bit of the sauce. Chop up a few vegetables (a chunk of pepper, a handful of peapods, or whatever else is on hand) and cook until just heated. Eat with a carb (some bread, rice, or noodles). Delicious!