Twitter

http://www.gamesforchange.org/

This is a game based learning site that offers a variety to different topics such as Civics, Environment, Economics, and Education. These are addictive and visually stimulating games that can reinforce the learning done in primarily a social studies classroom.

http://www.freetech4teachers.com/2013/05/5-things-i-like-about-building-pln-on.html#.UcH2P6zVDL8

Here are some "How To Videos" on using Google+

http://www.freetech4teachers.com/2013/06/four-google-how-to-videos.html?utm_source=feedly&utm_medium=feed&utm_campaign=Feed%3A+freetech4teachers%2FcGEY+%28Free+Technology+for+Teachers%29#.UcH1CazVDL8

Here is a blog article that was written by a teacher who is working with teachers about making their own PLN's. This is another option, other than using Twitter.

http://plpnetwork.com/2012/04/20/growing-your-pln-with-twitter-2/

This article published in Powerful Learning Practice is designed for beginners in the world of PLNs.  The article is divided into ten sections, each targetting a practical approach to using Twitter:  creating a user name; additing a photo/profile; keeping abreast of what is trending in education; not taking it personally when not everyone you follow follows you; challenging, expanding, and sharing educational philosophies and pedagogies; knowing what to do when 140 characters is not enough; recommending educational resources; finding and entering contests; downloading the Twitter app; and sharing posts by clicking "ReTweet."     SPM