eThemes has a few themes that may help teach this topic including Teaching Tips: Digital Citizenship, Cyberbullying, Ethics for Students. Check the eThemes A-Z listing or search to find more.
Cybersmartcurriculum.org offers teacher K-12 lesson plans to help teach about the topics of Digital Society, Digital Rights and Responsibilities, Digital Safety and Security, Digital Etiquette, Digital Laws and Ethics, and Lifelong Learning. Lessons are identified by the grade level appropriate for each activity, whether they can be done without a computer or if they may include a web 2.0 tool, and if they require an Internet connection.
BrainPop has a whole group of videos (with additional activities and even quizzes) to help teach students about Digital Citizenship including Copyright, Plagiarism, Online Sources, Digital Etiquette, and many more.
Or check out this Digital Citizen Resources LiveBinder created by computer teacher and blogger, Vicky Sedgwick. The LiveBinder includes TONS of links and resources for teachers, parents, and students interested in learning more about digital citizenship.
What might be some of your favorite resources for teaching digital citizenship?