Our view of ubiquitous computing is artefact-centred: in this view, computers are considered as secondary artefacts that enable items of everyday use as networked digital artefacts. This view is expressed in an artefact computing model and investigated in the Mediacup project, an evolving artefact computing environment. The Mediacup project provides insights into the augmentation of artefacts with sensing, processing, and communication capabilities, and into the provision of an open infrastructure for information exchange among artefacts. One of the artefacts studied is the Mediacup itself, an ordinary coffee cup invisibly augmented with computing and context-awareness. The Mediacup and other computeraugmented everyday artefacts are connected through a network infrastructure supporting loosely-coupled spatially-defined communication.