Are the leftovers from making stock good for anything?

I would dump them, with the caveat that some chefs reserve bones for making a second, lighter stock. I've only heard of this being done with Veal, so your mileage may vary.

I've also heard of people combining stock and chicken salad making by throwing a whole chicken in to the stock pot, then using the white meat for salad.

This offends me on many levels, but I'll just say that it probably makes for bad chicken salad, and also almost certainly makes for cloudy stock.

If there's any flavor left in chicken meat on the bone, or much collagen left in the bones after stock making, I'd say it hasn't simmered long enough. The stock should be both flavorful and unctuous, which means the meat will be flavorless and the bones brittle. Overnight is great for this, at a very low temperature - but with aromatics added later.

If you boil your stock, the tiny orifices in the bones from where collagen leaches will be sealed off, and the result will be much thinner than it could otherwise be.

I actually Googled this myself because I was wondering about the same thing. Someone else also suggested pureeing the veggies and adding them to spaghetti sauce. http://vegetarian.betterrecipes.com/vegetable-puree-leftover-vegetables-after-making-vegetable-stock.html

I recently made vegetable broth and used the leftovers as the base for a creamy potato soup:

I threw out onion skins and bay leaves, but kept the rest and added an equal weight of potatoes, water to cover, boiled and seasoned it, blended, and simmered with cream.

Simple, efficient.

I pureed all the left over vegetables, added garlic powder, Adobe seasoning, salt, pepper and Italian seasoning. Oh, and a little powdered chicken bullion. Put in bowl and topped with dollop of sour cream. Yummy!

Made stock last night with chicken carcass and assorted vegetable and fruit peelings. Used an InstantPot for 2 hours at high pressure. Separated and saved the clear stock.

Looked at the remaining solids, and reached for the hand blender. Added water and pureed the lot, including the bones. Gave it another 15 minutes at high pressure in the InstantPot.

A thick, smooth, opaque, dark brown, strongly smelling paste came out. Picture a concentrated sauce, or a liquidy pate. Judging from the aroma, probably too much orange peel this time around :)