In the information age, students must learn to navigate and evaluate an expanding network of information. Highly effective teachers model this process of information analysis and knowledge acquisition by continually learning through collaboration, professional development, and studying pedagogical techniques and best practices. Many teachers have extended their learning by developing online professional learning networks (PLNs). PLNs connect teachers to other individuals worldwide who can offer support, advice, feedback, and collaboration opportunities. PLNs also allow teachers to collect information from various Web sites and access it in one organized area so they can efficiently stay up to date on the latest teaching techniques, pedagogies, and changes in the field of education. This paper reviews three popular PLNs created for educators--Edmodo, Classroom 2.0, and The Educator's PLN--and provides an analysis of how teachers use the PLNs for learning, sharing, and communicating. (Contains 5 figures.)