Rice Mix
Make up some white rice. Either make some additions on the side to mix in (shrimp, veggies, etc) or mix in any leftovers that you want (beef cut-up, chicken, veggies..) Add in some complementing broth or gravy.
This is a great way to stretch leftovers if you don't have enough to feed more than one-two people!

Another leftover favorite: potato pancakes! Fry up some leftover mashed potatoes. Add in bacon, chives, onions, whatever you want.