In this paper we propose a novel way of supporting occasional meetings that take place in unfamiliar public places, which promotes lightweight, visible and fluid collaboration. Our central idea is that the sharing and exchange of information occurs across public surfaces that users can easily access and interact with. To this end, we designed and implemented Dynamo, a communal multiuser interactive surface. The surface supports the cooperative sharing and exchange of a wide range of media that can be brought to the surface by users that are remote from their familiar organizational settings. Keywords Large interactive surfaces, multi-user interfaces, sharing, exchange, collaboration