Peer-to-peer systems recently captured the attention of practitioners and researchers as they provide an attractive alternative to client-server architectures. Peerto-peer enables the creation of massively distributed networks of data repositories that can be setup and discarded easily according to applicative needs. Nevertheless, the current popularity of these systems is due mostly to their use for file sharing over the Internet. In this paper, we argue that the advantages of a peerto-peer architecture reach well beyond the realm of Internet file sharing. In particular, they become key in supporting enterprise processes and especially collaborative work involving mobile users. To support our view, in this paper we report about the design of an architecture and a core communication middleware in the EU project MOTION, where a peer-to-peer architecture is exploited to support collaboration among mobile and geographically distributed users.