Three meals from one roast
I did this with a pork roast, but beef would work well. I guess even chicken or turkey might as well.
First night, pork roast. Take leftovers and remove all fat. Divide in half.
Simmer one half with taco seasonings, diced green chilis, a diced fresh jalapeno if you like the heat, and a little chicken or veggie stock until you can shred it with a fork. Great as a taco/burrito filling, in mexican casseroles, enchiladas etc.
Simmer the other half with ketchup, brown sugar, a little vinegar, and spices (or some bottled barbque sauce of your choice) until you can shred it with a fork. This can be piled on buns for bbq pork sandwiches.
Both of these freeze well to use later, great for "quick" lunches.