Chats and Forums

Be "Tween" talk
Includes games, tournments, quizzes, and dynamic discussion for kids 9-12 years old.
http://betweentalk.com

Code Lyoko TCG
This forum serves as a fan-made trading card game for the Code Lyoko TV show.
http://codelyokotcg.com

CurvedSpace
Includes games, multiple chats, forums, and jokes.
http://www.cspacezone.com/

IntrepidEntertainment
Message board community with topics such as movies, videogames, and computers.
http://www.intrepidentertainment.co.uk

KidsChatters
Variety of chat rooms for kids. Paid registration required.
http://www.kidchatters.com/

KidsCom
An educational and entertaining site for kids 4 to 12. Games, monitored chat, and a creation center.
http://www.kidscom.com/

Open Site Public Forum
Message board of the Open Encyclopedia Project. Offers social and topical discussions.
http://open-site-talk.org/

YouthNOISE
Nonprofit affiliated with Save the Children Federation, provides teens with a forum to express themselves and take action. Includes message boards and e-mail.
http://youthnoise.com