The internet has dramatically transformed social space and time for many people in many different contexts. This dramatic warping of the social fabric has happened slowly over time as digital technologies have evolved and internet speeds have increased. While we are all aware of these changes, the impact is often little understood. There are few monographs about social groups made possible by the internet, and even fewer about educational communities made possible through digital technologies. Inside Mathforum.org details the ways that digital media are used to enhance the practices that teachers and students of mathematics engage in. The book also shows how different kinds of mathematical conversations and interactions become possible through the digital media. Unlike many other educational uses of digital media, the Math Forum's community has provided online resources and sustained support for teachers and students, and it leads the way in showing the power of digital media for education.