Place three cups on the tables or desks of groups of students working together. Mimicking traffic signals, green cups are on top, followed by yellow, and red at the bottom. Whenever groups or tables are talking quietly, they may have the green cup displayed. If they begin to get too loud, walk over and place the green cup at the bottom and the yellow cup will signal that they have a warning for their noise level. If they correct their behavior, they get their green cup back on top. If, however, they do not correct their noise level, the red cup moves to the top. Red signals that they go to silence.
What I like about this is that it's pretty cheap to construct and it's simple for students to understand. Best of all, the teacher can simply walk by a group, silently move cups, and communicate exactly what students should be doing. If groups are in centers or playing a game, this would be a useful management idea.
imagecredit: The Mailbox