At BarCampDC today -- a "ad-hoc unconference and is part of the larger BarCamp movement. While there are topics suggested for discussion, there is no set agenda until everyone gathers. Attendees are required to participate to some degree: either by giving a presentation, demo, etc. or by facilitating a group discussion."
This gets back to the unconference model related to the Open Space Technology at General Assembly. But I think it works better here. And I think a lot of GA regulars would have a hard time with it.
More about that and its Unitarian Universalist application later.