The World Cafe model: Everyone wears a name-tag. The room breaks into groups of five. A question is put up on the board. Each group table has a large piece of paper-- large enough for everyone to write or doodle on. The group spends 15 minutes deliberating on the question at hand. When time is up, 4 people leave to find new tables, while the 5th stays behind-- this person is now the "table host". New groups of 5 are formed. The table host takes the first 5 minutes to debrief the new group on what the old group discussed. Then a new question goes up on the board, and the pattern repeats. When finished, the table hosts present the results to the whole group, and then the floor is opened for discussion.
A variation on the model: Everything as above except that instead of the same question being discussed by every table, each table has a unique question that stays with that table. The table host is responsible for taking notes and compiling information.