Overall, I found Common Sense Media and iKeepSafe to be the most comprehensive and most helpful on all things including online, video, cell, movies and television.
Common Sense Media
The Department of Health and Human Resources developed the Stop Bullying Now site which covers more on "traditional" bullying:
Stop Bullying Now
Great site to check out before your child buys a video game:
Entertainment Software Ratings Board
This is a short list. Feel free to leave a Comment with additional suggestions. Hope this helps and remember...
IT TAKES A VILLAGE!