Second hand swapping is growing more and more popular. I have a feeling this is a result of a combination of people wanting to reduce the number of items they purchase, buy items at lower prices and make a little profit off the things they have and no longer want. I don't have any hard science research behind those statements though, just thoughts to guide further investigation.
Until then, you can try out some second hand swapping at these various places:
Book Mooch, which allows you to swap books with others online.
Swap at Home, allows you to swap anything. It's a little confusing to me how this works.
Ikea furniture swap organized at their store in Amsterdam!