Our research on knowledge management is rooted in the community perspective. We believe that knowledge systems should serve primarily to help people create and share new knowledge. But we also acknowledge the role of stable, structured and reliable information, both as a component of our systems and as a component of the organizations within which we work. The contribution of the paper is a framework for integrating organizational and community perspectives on knowledge management and its computational support. Our basic idea is that knowledge is not a static chunk of information, but rather, knowledge evolves in a cycle of knowledge liquidization and crystallization. The evolving process takes place through the interactions among conceptual worlds, representational worlds, and the real world. This paper first describes the knowledge liquidization and crystallization framework. We then illustrate the approach with three systems, Knowledge Nebula Crystallizer, livingOM, and ART-SHTA.