Really Really Free Market
A Really Really Free Market (RRFM) is a popular form of gift economy in USA. The UK equivalent is a Give and Take, and the South American equivalent is the Gratiferia. An RRFM is primarily an arrangement where people bring things to give away and allow strangers to take what they fancy and/or give whatever they brought to give away. Many RRFMs go beyond this to include goods as well as services, so people do thinks for each other for free as well, such as teaching, repairing, making music etc. An RRFM has been called a 'temporary autonomous zone'.
Depending upon how many people come along, a large public space may be needed. If it has high visibility and other positive social associations, even better - often RRFMs are held in public parks. Some under cover space is a wise precaution if the weather is unpredictable. People generally bring a tarpaulin or blanket to spread their items out on the ground. Paying for space should be considered a last resort, though some groups have done this - funding the RRFM through donations - often as a temporary measure until they get a better venue, or perhaps until there are enough attendees to negotiate a better solution.
This may be the most important single factor behind organising a successful RRFM. To start it off, use Email, social software, hand-out fliers, contact local radio stations, post posters, take out ads in local newspapers and do whatever else you can think of to let people know what is happening. You may find that RRFMs appeal to a generally younger audience, but don't assume this -- the more different groups of people who come along and mix the better. Unless they've seen it or heard about it first hand, many people will often not have a clear idea what to expect. A regular, predictable schedule is good - for example, on the first Saturday of every month. This allows for a gradual build of attendees as people tell their friends about it and invite them to the next one. Some people will take time to think about which items they could bring to give away or to get up courage to come back and carry out services for strangers for free.
Often a political or social organisation - such as a 'Critical Mass' may decide to hold an RRFM - often with the aim of promoting community and establishing horizontal links with like minds and groups.
Running The RRFM
Starting off the RRFM requires a consistant input, but once if has got going, it should be self-managing. Be flexible, ready to adjust what happens to the particular locale and the personalities of the people involved. There may be issues arising such as about the venue or reaction of authorities, but these are generally fairly easily resolved. Occasionally some key decisions may need to be clearly made, such as if the schedule or venue need to be changed, in which case it may help to have a core team of organisers, but generally loose-knit, horizontally organised self-management is simpler and more effective.
According to Wikipedia, the name "Really, Really Free Market" was coined in USA in about 2003 by "anti-globalisation" protestors. This makes it considerably newer than its European equivalent, the Give and Take (started in Wales in 1989) or Food Not Bombs (started in USA in 1980).
Argentinian Ariel Rodríguez has been spreading the idea since 2010, using the slogan "Bring here what you want, (or nothing), and take away what you want, (or nothing)".