Knowledge Management (KM) is one of the key progress factors in organizations. It aims at capturing explicit and tacit knowledge of an organization in order to facilitate the access, sharing, and reuse of that knowledge as well as creation of new knowledge and organizational learning. We introduce in this tutorial knowledge engineering techniques that help at structuring information and knowledge and we present techniques defined in CSCW to handle design rationale and negotiation. An example of collective knowledge is then defined: Project memory. Approaches that help to keep track project knowledge are then detailed. We extend our tutorial by presenting multi-agents techniques and the socio semantic web approach which helps to represent concepts built collectively in an organization. These approaches can be illustrated in real applications in several domains: design, safety, marketplace, etc.