CSM is a leading force in digital citizenship. It has an entire curriculum for free and tons of other goodies. It is a first stop.

Flocabulary is a music video company that makes tween videos about social issues including digital citizenship. They do a great job. They were recently purchased up by CSM.

This link will give you a series of articles and videos about Digital Citizenship and how to teach / talk about it with kids.

Videos, articles, games. NSTeens is directed towards more of a middle school / high school demographic.