Goodwill & curb, both good ideas.
A couple years ago I put an old mower at the curb. It still worked but had very little power, probably down form the original 3hp to about 1hp.
. I got it free, so, worth every penny! But it had a couple issues. It was so light weight (magnesium deck, ask me how I know
) that you had to step on top of it while cranking, and it would only run off the top half of the gas tank as the lower pickup wasn't picking up.
A few hours later a kid from up the block ran to it, looked around as if to see if anyone was watching and made off with it like a bandit. Good, it was gone. Later that evening I looked out to see him sneaking it back to the end of my driveway. RATS! it came back.
Then I put a sign on it saying "Works, here's how..." and it was gone within an hour to a brother in a Cavalier.