This document discusses open education and knowledge building communities. It notes that open source is an institutional and social innovation, not just technological. It calls for an "ecology of experiments" to support learning. Key aspects of knowledge building communities identified include building social networks, developing capabilities, and ensuring sustainability. Examples provided are the Urban Universities Portfolio Project, Carnegie Academy for the Scholarship of Teaching and Learning, and the Inter/National Coalition for Electronic Portfolio Research. Intermediaries are seen as important to support open education through knowledge building within social groups and sharing more broadly. Formative assessment and technological support for communication are also discussed as means to ensure the sustainability of open education initiatives.