We actually exchange all kinds of stuff over on my other site. We have a whole section just for buy/sell/trade. It's a parenting site so the majority of stuff is kids clothes and it's no different than going to a thrift shop only it's online, you don't have to dig through anything and it conveniently shows up on your doorstep. Plus you get to know the ppl online pretty well so it's not like it's coming from a complete stranger.
It's a very good way to recycle.