What is a PLN and how do I start one? I love this intro to the concept by John Spencer.
Things he mentions that are worth noting and exploring:
NING--network of educators interested in sharing information
Twitter--I have heard many at conferences say this is their #1 source for professional development!
Social Bookmarking sites Diigo and Delicious. These allow you to share sets of bookmarked favorites with other like-minded individuals.
Blog--Blogger and Posterous are two that are pretty easy to navigate. Edublogs is another great one that specializes in educational applications.
Teacherlingo--website for sharing information, selling lessons, linking to other blogs
ISTE: the big national organization that tracks, gathers, documents, promotes technology-related learning and research