This concept of a PLN  has been around for many years. What has changed in recent years though is the reach, the size and the availability of that network.
From your colleagues in the building you work in, a cherished personal mentor, professional development opportunities offered sporadically throughout the year, conferences and college credit classes taken for re-certification to blogs, RSS feeds, Twitter, Nings, and Skype among others.

Learn how to be in charge of your own Professional Development, connect to learning opportunities around the world, and about  tools that enable you to make a 21st century Learning Network possible.