Fishbowl discussions and Socratic seminars are a great way to have students articulate their ideas and further develop an argument. The teacher is fairly passive in these class discussions as they ask an open-ended question and may intervene when the discussion is lacking, but the students control most of the exercise by refuting or expanding upon statements made by their classmates and asking follow-up questions.
The setup and rules for Socratic seminars and fishbowls vary, but the basic idea is that a smaller group of students in the center of the room discuss a topic, while other students in the outer circle observe them and take notes or create additional questions. However, this outside group is limited in their ability to participate in the discussion.
That's where todaysmeet.com comes in. TodaysMeet is a site that allows users to easily create chat rooms with no sign up required for the participants. Rather than having the outside circle take notes and be silent observers, they can participate in a chat room about the inner-circle discussion. Within this chat room, they can respond to statements made in the inner circle or to comments made by other students in the chat room. This strategy turns students who are partially involved in the discussion into active participants and contributors.
From my own experiences, I have learned that students do need to be reminded of your expectations for the chat room discussion. It will create more work on your end to monitor the chat room while also paying close attention to the verbal discussion, but if the major drawback of a strategy is that it leads to too much student participation, then I'd say it's a winner.