Recent technological advances have made it easier to communicate over distance and time. However, most of these technologies were initially designed for one-to-one communication, which makes them hard to use for group communication. Creating and maintaining shared lists of contacts is hard. Using these lists with different applications is usually impossible due to incompatibilities between them. In this paper, we present Circa, a software infrastructure that was designed to help people communicate with small groups of people such as close friends, colleagues or relatives.