Collaboration flow management is a new paradigm for virtual team support which aims at assisting the opportunistic flow of collaboration within a distributed project, considered as a living and self-organizing system. Such a flow includes informal and formal, synchronous and asynchronous, task-oriented and project management-oriented collaborative sessions. Some of them are elements of model-driven session-based process fragments. The paper defines the collaboration flow management paradigm and describes our Java prototype of collaboration flow management system through a realistic scenario. The paper also discusses how a high level of flexibility is obtained through a set of design choices and object oriented implementation techniques.