Take Freecycle, for example. I came across Freecycle a couple years back when I was trying to declutter my life.
I had a lot of stuff that I didn't need... but it wasn't quite right for the thrift store basket. Like... unpainted, assemble-yourself furniture that never got put together; a bag of antique glass beads that I came by; partially used cans of quality paint. I think you get the idea. Anyway, I couldn't drop the stuff off at Deseret Industries because they'd either refuse it (mattresses, jeans with holes), or would probably break it (dishes), or would just have no idea what to do with it (cables from old computer set-ups).
Freecycle uses Yahoo Groups to connect givers with takers. How does it work? From the web site:
When you want to find a new home for something — whether it's a chair, a fax machine, piano, or an old door — you simply send an e-mail, offering it to members of the local Freecycle group. Or, maybe you're looking to acquire something yourself. Simply respond to a member's offer, and you just might get it. After that, it's up to the giver to decide who receives the gift and to set up a pickup time for passing on the treasure. Our main rule: Everything posted must be free, legal, and appropriate for all ages.
You can find (or start!) your local chapter using the Freecycle site.
I belong to the Salt Lake City chapter of Freecycle.
Hattip: PSFK and A Green Idea, who reminded me that not everyone knew about one of my favorite web tools.