What to do with old tires? I recently upgraded to puncture resistant tires on my road bike. The previous tires are old, but still usable. Is there any value to doing anything other than throwing them out? For instance, is there any reason to keep them? Is it possible to sell used tires? If no one wants them, can/should they be recycled?
I usually gift them to people who need them.

Edit: To expand more on my answer, I use rather expensive tyres and I want them in mint condition. So after a couple of months I'll most probably change them. The old tyres can still give 6-12 months of quality riding time to someone. So I'll post on local riding forums with closeup photos of the tread and usually people will get them.