This document discusses learning communities and theories related to 21st century learning. It covers educational theorists like Dewey, Piaget, Vygotsky and their socio-constructivist views on learning. Communities of practice are examined, with a focus on how participation and collaboration within a shared domain can support cognitive development. Examples of online tools that can facilitate communities include wikis, blogs and social networks. The document advocates that awareness and access to these tools and communities can help develop effective learning environments.