Businesses increasingly provide and use services, applying formal (Web) services technology for the description, composition, and management of software as services. At the same time, social communities are emerging on the Web, applying less formal practices and Web 2.0 technology for the dissemination and aggregation of diverse content. In this paper, we are interested in the combination of these two trends in the form of service communities: social and business communities exchanging services. We discuss applications of service communities and introduce the concept of Service Clubs as a structuring mechanism for communities. Clubs have been specifically designed to support community-based, per-project interaction and composition of services. Categories and Subject Descriptors D.2.12 [Software Engineering]: Interoperability