This paper explores the nature of integrated networks of practice, and in particular, the important role of "hubs" within networks. Hubs are individuals or groups that energize cross-connections, improve knowledge flow, enhance learning across small clusters of expertise, and play critical roles in building and sustaining robust integrated networks. Three examples illustrate how group-based hubs can facilitate professional learning across naturally occurring significant networks. Drawing on these examples and scholarship in the field, we offer a comprehensive framework for cultivating integrated networks for teaching and learning, and highlight some of the lessons we have learned.