I don't know about anyone else, but when I make soup there's usually a cup or so left over. Not enough for anyone to be bothered warming up, but what a waste to throw it out! So, this is what I do:
Mix leftover soup with some broth (any kind that will complement your original recipe eg/veggie, chicken, beef...), and make sure it's enough to cover the bottom of a casserole pan. Pour the soup into your pan, and heat in the oven at 400F until it starts to bubble. This shouldn't take very long, so while you're waiting, mix up a batch of biscuits, using 1/2 cup more liquid than usual. When the soup is bubbling, pour biscuit dough over the top, place back in the oven, and bake until the biscuits are done- 20-25 minutes.
This is good with any type of soup I've tried it with- veggie, noodle, even a cream soup. If it's leftover chili or even a minestrone that your dealiing with, you could use the biscuit dough or just top with a cornmeal muffin recipe. It's easy and tasty, and perfect for a quick lunch or dinner.