I've seen towns have "waste" days. Paints, oils and other liquids are collected and disposed of. Usually see them in the spring but your town hall might have more info Posted from my iPhone/Mobile device
I flagged down our G-man yesterday and asked him. He said you can use kitty litter to dry it out or Lowes sells paint hardener which I understand is a powder you can add which is supposed to quickly harden the paint. Then you can leave it out with the lid off the can and they'll take it.