One fabulous thing about cooking a big turkey, or chicken, is the leftover bones. You can make a big pot of soup from practically nothing, if you just start with some good bones. I didn't even have a whole carcass to start with and I made a wonderful pot of Turkey Noodle Soup for dinner this week.
As soup is often less of a recipe than a process, and I'm sure you've made your own soup before, I will just tell you what I did. I started with four turkey drumsticks that had been fairly well stripped of meat (it looks like the meat is mostly gone, but there is still a lot left -- in between the connecting tissue and small bones). I offered my turkey carcass to my aunt, and so I used the four extra drums that I bought, roasted, and were leftover (I think Peach picked on one of them, but the other three were untouched except except for me stripping the meat for leftovers).
I covered the bones with water in a large soup pot, I placed it on the stove, covered with the lid cocked to release some steam, brought it to a boil and then lowered the heat so the water would simmer for about 90 minutes to two hours.
After the 90 minutes were up, I removed the bones from the water to a platter and strained the broth. I placed the broth back on medium heat and added half an onion, diced, and three carrots, diced. You can add celery here also, but my family balks at celery (puh!). I salted it and peppered it and added 1/2 t. dried thyme. I simmered it until the veggies were tender, about 30 minutes.
While the veggies were simmering, I pulled the rest of the meat of the turkey bones. There is always a little more meat attached that loosens up in the boiling. I diced the meat into little pieces.
After the veggies cooked, I added a couple palmfuls (probably 2 T. total) soup base -- 2:1 chicken to beef (the beef I add for turkey soup, because turkey soup has a deeper flavor than chicken soup). You can also use veggie base for a varied flavor. If you don't have soup base, you can use canned broth, but you may need to salt your broth more. (Sometimes I add a quartered onion, a couple stalks of celery and some garlic cloves to the original cooking water, and then the broth is more flavorful and often doesn't need the base -- I was lazy the day I made this soup.) I added about 1/2 t. onion powder also for a concentrated onion flavor. After the soup base dissolved and I tasted it and adjusted the seasoning (usually just salt and pepper), I added the turkey back to the broth and a cup (or more to taste) of fine noodles, cooking a few more minutes until the noodles were done.
This soup is practically cost-free (what's a half an onion, three carrots and a cup of noodles cost?) since the turkey was leftover from another meal. It's also very low in fat, because the only fat was on the leftover turkey, most of which went into the garbage.