Although a plethora of Web 2.0 applications exist today, there is little literature reporting on experiences, concrete recommendations or best practices when developing such applications. The scarcity of such records makes it difficult for developers to determine how best to support the practices of communities with the use of Web 2.0 technologies. In this paper, we report on thirteen practical lessons learned while developing Web 2.0 collaboration services for Communities of Practice in the framework of a three years long European research project on Technology Enhanced Learning. The main objective of this project was to investigate how Web 2.0 technologies could impact the communication and collaboration needs of Communities of Practice interacting online and, conversely, how new interaction needs could impact Web 2.0 technology. The above lessons are presented in a way that could aid people engaged in various phases of the development of Web-based collaboration support services.