A few friends and I are working on a website called swopspot.
On swopspot you can trade anything. One hour of gardening for a dinner, old CDs for new books, handmade items for useless things. Just add stuff you want to trade away to your profile and wait for someone to make an offer to you. Or you browse around, see what your neighbors are willing to give away and make them an offer.
Swopspot enables you to trade locally. You save on packaging and delivering because in the best case you just meet for a coffee to finalize the trade. Giving the environment a fair share as well.