Leftover vegetables can be transformed into a delicious stir-fry. Simply heat some oil in a pan, add the vegetables, and stir-fry until they are heated through. You can also add leftover meat or tofu for added protein. Season with soy sauce or other sauces of your choice, and serve over rice or noodles. Another option is to blend the leftover vegetables into a tasty leftover vegetable soup. Just puree them with some broth, seasonings, and perhaps a touch of cream for a creamy finish.