The Idea of Open Space Technology is to give a very basic structure that encourages and allows for Self-Organization on a large scale. It is done with groups of 5-500 people, in corporate setting, local government and many large scale NGO's wanting to ask a really big question and allow for knowledge and wisdom to come from everybody involved.
Open Space invites anybody who wishes to suggest a topic, question or debate they have both passion and responsibility for. Than, a market place of ideas, times and locations ties it all together. People are then let loose and go (or don’t go) to whatever interests them.
This is a beautiful radical method which gives a lot of freedom and invites surprises and massive breakthroughs, while collecting written knowledge of all the different conversation going on. There are also Bee's and Butterflies. 

Harrison Owen created Open Space in the early 80's, and nobody explains it better than him, in his book- Open Space Technology: A User's Guide - Harrison Owen.  There is also a short version.