Winter squash is always a great soup base. Sauté some leeks or onions and add other appropriate leftover veggies, including sweet potatoes and roasted veggies. Toss in that turkey stock you made. If you have any sage left, it goes beautifully with squash. Other herbs do, too. Add a hot chile pepper and some garlic. Put some coarsely chopped up greens in at the end; they don't need long to cook and the orange and green together is just beautiful. Variations include using miso, cooked beans, and ginger. Go wild!
Leave chunky or purée all or part of the soup.