Ning is great website where you can create your own social network, similar to sites like MySpace or Facebook. You may be asking why you would want to do that. Well, besides the fact that MySpace and Facebook is probably blocked at your school, both of those sites have questionable security and privacy issues that simply would not plague you if you chose to use a Ning. Your Ning could be a site used by your class as a social network to safely debate or discuss different topics relevant to your class. Nings can be made public or private, so you can limit exactly who can see and connect with your network. Also, educators can use Ning free of charge! For more educational uses, read this.
To use Ning as a part of your PLN, it would be incredibly easy to set one up and invite collaborators to join. You could share web resources, attach files or discuss issues of pedagogy. The best way to get to know the features and benefits of Ning is to experience it yourself. Chances are, whatever your bailiwick, you'll be able to find an educational Ning that is already set up and running. Most of these are public so you can join the network. Here are some that I'd recommend:
The Educator's PLN
Ning in Education
English Companion Review (Award Winning)
EFL Classroom 2.0 (Award Winning)
Country Day School
Here is a video explaining Ning in Education: