I put my chains in a baggie and put in the recycle bin. I assume that a baggie over a greasy rusty chain is recyclable, as I assume they pull steel out of the pile with big magnets. I have not checked with the recycle center.
A long chain that can tangle up on other stuff could be a hassle for the sorters at recycle centers, a baggie prevents that.
I once saw a photo of someone using an old bike chain to make boot cleats for hiking on ice, I tried it and it was a dismal failure. Don't bother trying it, the lack of sharp points prevented it from digging into the ice.
ADDENDUM:
Found the photo:
