This document defines and explains personal learning networks (PLNs), which allow individuals to extend their learning outside the classroom by engaging with others online. A PLN involves connecting with people who can guide one's learning by sharing knowledge, resources, experiences and answering questions. Benefits of PLNs include learning new things, collaborating, getting validation and building camaraderie. Various online tools that can be used to build a PLN are described, including Twitter, Diigo, 際際滷Share and Flickr. Maintaining a PLN is important for teachers to stay current and teach in a way that engages students.