I paid for the ammo - brass case and all, so I'm taking it with me! Any brass that it left by shooters that don't cleanup - I take it. As long as it's not in the barrel. I even take .22 and steel cases. Even berdan primed.
If it's metal - then it has value. I have hundreds of 38, 9mm, 40, and 45acp, and I don't even own a gun in that caliber - but I know one day I probably will. I keep them all separated in plastice bags. Anything not reloadable I put into a "brass," "aluminium," or "steel" bucket because scrap brass is $1.50/lb, aluminium is $ .80/lb, and steel is $.05/lb (steel is also the heaviest, and I have scrap bins from welding and plasma cutting)