You will see EdCamps mentioned on Twitter. They provide free professional development and are a way for educators to get together, set the agenda for sharing that day, and then attend break-out groups. At the end of the day, at the Smackdown, attendees voluntarily show a favorite Web 2.0 tool or similar computer application. Even if you don't attend in person, you can follow along through the chats, on Twiter, using the hashtag. For instance, this August, an EdCamp was held here in Connecticut, where I live, and the hashtag on Twitter was #edcampct. Yes, they are an excellent way to collaborate in-person on online. At the EdCampCT, for instance, I saw a wonderful demo of how a social studies teacher from MA uses video in his teaching, for mock debates and so forth. One of the national organizers of EdCamps, Dan Callaher (? think that is his name), also did a presentation on the concept in general of what are the best forms of professional development. Perhaps others can chime in on the benefits of EdCamps.
I am learning how to create and develop PLN in my college class. Some ways we are developing ours is by using Listserv called QIAT. The website is: http://natri.uky.edu/assoc_projects/qiat/listserv.html. This is a email collaboration system. Here is also a website that talks about PLN and Twitter: http://whatsnewintheworld.net/2010/01/twitter-as-a-pln/. I also think that you might find some blogs helpful. Here are some that I have looked at: http://www.onlinedegrees.org/top-40-special-education-blogs/.
I hope this helps,