Try Nike’s Reuse-A-Shoe! It’s an effort to keep shoes out of landfills by recycling them and putting them to good use in basketball courts, playground surfacing, tennis courts… They use the rubber from the soles, the foam from the insulation and padding and the cloth from the shoe uppers to pave the way for sports and outdoor play.
So of course, when you’re cleaning out your closets, donate gently used shoes to a charity you find worthwhile. But for those athletic shoes that have seen better days (you know the ones I’m talking about), go to Nike’s site to find a drop-off location near you. They have them in most metro areas.