Social relationships between co-workers, family members and friends play an important role in our everyday lives. They are responsible for our well-being, for a productive working atmosphere and for feeling part of our various communities. Nevertheless, it can be difficult to establish and maintain such relationships if individuals are spatially separated, e. g. working in different branch offices of a corporation, as they usually cannot interact and communicate in a natural, everyday manner. In the past, significant effort has been put into the development of planned, explicit interaction methods such as email, chat or video-conferencing. In contrast to that, much less is known about techniques to enable casual, spontaneous interactions between spatially separated social groups, e.g., occasional meetings on the office floor, by the means of implicit and more subtle methods. SISSI 2010 brings together academia and industry to present new ways of facilitating, establishing and maintaining social relationships by the means of ubiquitous systems, in order to achieve a feeling of togetherness, presence and closeness between members of spatially separated professional or private social groups. The audience of SISSI is interdisciplinary, including researchers from human computer interaction, pervasive communication, spatial cognition and communication sciences.