Understanding Child Development can help with parenting a child.
The CDC offers good factual information:
http://www.cdc.gov/ncbddd/child/
PBS has good factual information and tips for activities:
http://www.pbs.org/parents/childdevelopment/
This site offers an overview of the Adolescent Brain.
http://www.pbs.org/wgbh/pages/frontline/shows/teenbrain/
The Alzheimer's Association has a wealth of information and resources to assist professionals and family members.
The Anxiety Disorders Association of America has good information about Anxiety and concurrent conditions like depression.
The National Institute for Mental Health has a good deal of factual information on Depression.
http://www.nimh.nih.gov/health/publications/depression/complete-index.shtml