Really really free market
From Trashwiki
The idea behind the Really Really Free Market (RRFM) is similar to freeshops, but the groups of people organize periodic "market days" in city parks or other open spaces. Participants are encouraged to share unneeded items, food, skills and talents (entertainment, haircutting, etc.), to clean up after themselves and to take home any of their own items they were unable to give away during the event. In other cases, used goods are picked up from the donors' homes, thus eliminating overhead costs. Donors are often not motivated by financial need or strictly anti-capitalist conviction, but by a desire to get rid of what would otherwise be garbage without adding it to landfills.
A benefit of a RRFM is that it allows people who are struggling financially to save money on things they would otherwise have to pay for, and they can have money for other important purchases.
Anyone can organize a RRFM event. Here is the list of RRFMs already taking place in differents parts of the world: Really Really Free Market
There is also a group on Couchsurfing: Free Market: Trade, Swap, Borrow, Lend, or Give Away
