Obviously, you are going to want to try this leftover meatloaf sandwich recipe first. If still looking for more ideas, think of using leftover meatloaf as you would meatballs (meatloaf is akin to one giant meatball, after all). Try it crumbled on top of a pizza (Whole What Pizza Dough is so easy), or crumbled in a vegetable soup, such as Minestrone Soup, to add some protein.