For $5 I think I'll list it on my company forum for exactly the same price. I'd much rather the battery, which may very well have a few years left in it, go to someone who needs it than to be recycled.
If no one takes it (people tend to be wary of deals too good to be true) I'll keep it in the basement, off the deck, and keep it up with a maintainer once per month or so. I'm not sure I would use it for the purpose of jump-starting, but who knows. It could certainly help with boosting a weak battery on a very cold morning, when I really have to get to work.