I love to make leftovers turkey soup out of turkey and stuffing that is pureed with curry powder and peanut butter. You can thin it out with a cream sauce or chicken/turkey stock. It sounds really over the top at first, but it is deeply influenced by Ethiopian and African cuisine. It is so tasty, I fear you will become addicted to its flavor.
It is also really good to make quesadillas or pasties from leftovers. Take the lamb, the chicken, the beef, or turkey and dice it up, add it to a mirepoix and throw it in a nice pastry dough to make a pastie. Or add cheese to it instead and make a nice calzones.
I use these leftovers as my experiments. I make different kinds of doughs and different stuffings each time. When I find one that works, I commit that one to memory. Most folks end up throwing this stuff out anyhow.