When your headphones need to be replaced, the last place you should send them is in the trash can. The metals and plastics that make up headphones are recyclable. The company Think Sound accepts any brand and any style of headphones -- from the small in-ear pieces to the large on-ear style -- and recycles them free of charge. And for your good deed, the company will give you a coupon to take 15 percent off the purchase of new headphones from its site. To learn more, visit thinksound.com.