BAM! Body and Mind.
Questions and answers on health issues.
Includes games, quizzes and health tips.
From the U.S. Centers for Disease Control and Prevention.
http://www.bam.gov

Your Body.
From growing up to getting braces, popping pimples to catching some ZZZs, this site gives you the basics on your changing body - from head to toe.
http://www.kidshealth.org/teen/your_body/

Teenage Health Freak.
Reliable health information for teenagers organized by
two physicians in a contemporary, entertaining and informative way.
http://www.teenagehealthfreak.org