A key feature of ubiquitous handheld devices will be their simple usability in mobile and highly dynamic ad-hoc peer-to-peer environments. With LINDA, JAVASPACES and TSPACES, shared memory-based communication concepts have been realized on the system level with corresponding APIs. This article proposes to consequently use the same simple communication paradigm also on the user interface level. In this paper we examine existing basic technologies, analyze typical application scenarios and the underlying communication patterns. We discuss in detail, how these patterns can be realized with the InfoSpace mechanism which offers to each user a private local space and a view on a common space shared between all participants. Finally we show an architecture which realizes the InfoSpace infrastructure and report on first experience with a JXTA-based solution.