Another easy-to-make dish composed of Thanksgiving leftovers is a modified Shepherd's pie. Pretty good! 
Loosely based on this Rachel Ray recipe, I heated up leftover gravy, threw in shredded turkey, sauteed carrots and baby spinach in a little olive oil and garlic, and zapped the mashed potatoes in the microwave briefly with a splash of chicken stock to loosen it up. Then I layered it all (in that order) in individual casseroles. I sprinkled some grated Parmesan cheese on top of the potatoes and baked them at 375 degrees for about 15-20 minutes (until it was bubbly).