"What has started as a simple answer to the question "what are you doing?" has now developed into one of the most popular online social networking platforms with 255 million Average Monthly Active Users (MAUs) as of March 31, 2014 . The potential of Twitter in education is uncontested and the research literature in this regard abounds with accounts of teachers leveraging it in their instruction. Twitter is also a powerful medium for teachers professional development and below are some of the ways you can use it to enhance your PD."
Via John Evans