In this paper we study the collective dimensions of teachers' work in their ordinary daily practice. We argue that teachers' ordinary work comprises many collaborative aspects, and that the interactions with colleagues, often through resources, are crucial for teacher professional development. Using a theoretical framework based on teacher documentation work, we focused on interactions between teachers and resources to study two teachers' work: one teacher in France and one teacher in Norway. For both teachers we identified collective dimensions in their work with resources. Contrasting these two cases enabled us to identify particular features, but also possible invariants, of teachers' work with resources. Our results indicate that collective dimensions are always present in teachers' work, but that true communities of practice, which could be considered as an achievement of collective teachers' work, are scarce. We discuss the conditions for the emergence of such communities.