Netsmartz is a fun and interactive website to show kids the precautions they can take when they journey online.
Not only does this site include lessons and videos, but now there is a series of shows that your students can watch too.
Be Internet Awesome is a Google program that involves a fun and free web-based game called Interland. This is an educational curriculum to teach kids how to be safe and responsible online.
Common Sense Media has an entire curriculum devoted to digital citizenship. The free lessons are organized by grade bands from K thru 12th grade.