It's important to understand the distinction between recycling your gear and donating your gear. Recycling your gear means giving it to an authorized center where it's reprocessed into raw materials. Donating your gear means giving it to a person or organization that will use it, which lengthens the lifespan of the item. This distinction is important for safety reasons.
For example, you shouldn't donate used climbing rope. Rope must be in top condition for safe climbs. Most manufacturers advise that their ropes be retired after five years in service and/or 10 years after the manufacture date [source: Climbing.com]. Obviously, though, if your rope is shredding or damaged before then, it's time for a replacement. Recycling centers can melt down nylon climbing rope to make it into completely new products like carpet fiber, coat hangers, telephones and children's toys. Some companies that sell rope will also recycle it for you [source: Sterling Rope]. Check your local retail stores, too, for free return or redemption programs.
If you have old running shoes and sneakers lying around, Nike will take them off your hands. Its successful Reuse-A-Shoe program takes your old sneakers (any brand) and recycles them into an entirely new product -- athletic and playground surfaces. Adventure clothing like fleece, cotton tees and some polyester products are also recyclable through a program called Common Threads, implemented by the retail company Patagonia. You simply mail Common Threads your appropriate used clothing, and they recycle it down to make new clothing. Some of this recycled clothing also contains fiber made from recycled soda bottles!