Common Sense Education might just be my favorite digital citizenship resource. They offer a free Digitial Citizenship Curriculum split by age: K-2, 3-5, 6-8, 9-12. (Additionally, they offer a premium service for professional development but that is really targeted at the school level.) They have a whole set of unit lesson plans all ready for you to use in your classroom but if you want to check into a specific topic that is an option as well. So dive in and start teaching yourself, your students and others about digital citizenship today.