Group discussion with varying subsets of participants Source:
Place at least 4 and at most 6 chairs in a row so that they face the group. Explain the rules:
Take a bench seat when you want to contribute to the discussion
One seat must always be empty
When the last seat is taken, someone else must leave and return to the audience
Get everything going by sitting on the 'bench' and wondering aloud about something you learned in the previous phase until someone joins. End the activity when discussion dies down. This is a variant of 'Fish Bowl'. It's suited for groups of 10-25 people.