I took the SNA course by Lada Adamic in coursera. It's a super interesting course. In fact, I was using the networks only how a visualization tool, and that is what it make me little bit embarrassing because there are more, a lot of more. You can detect communities, know the more centric nodes and a lot of other information. So, there are a lot of reasons to look the course.
In this respositoy you can find the R code which create the networks, and export the data in json format.