We present a service providing real-time feedback to participants of small group meetings on the social dynamics of the meeting. The service visualizes non-verbal properties of people's behaviour that are relevant to the social dynamics: speaking time and gaze behaviour. The service was evaluated in two studies, in order to test whether the feedback influences the participants' visual attention and speaking time and enhances the satisfaction with the group interaction process. In a qualitative evaluation it was found that groups in general perceive the social feedback during the meeting as a useful and positive experience, which makes them aware of their group dynamics. In a second study, aiming at a more quantitative analysis, we obtained preliminary evidence that the feedback service affected participants' behaviour and resulted in more balanced participation and gaze behaviour. We conclude that services providing automatic feedback about relatively low-level behavioural characteristics can enable groups to adjust the social dynamics in group meetings.