Growth & Development from KidsHealth.org
Provides a wide variety of information on growth & development from infancy through adolescence.    Topics include sleep, growth, learning & playing, communication, and feeding & eating.  “Kidshealth is the largest and most visited site on the Web providing doctor-approved health information about children from before birth through adolescence.”
 

Zero to Three – Developmental Milestones
A browsable list of pertinent topics relating to infants and young children, plus a search option and a “frequently asked questions” section.  “ZERO TO THREE's mission is to promote the healthy development of our nation's infants and toddlers by supporting and strengthening families, communities, and those who work on their behalf.”
 

BabyCenter – Pregnancy & Baby Timeline
This site allows the searcher to choose the week or month of pregnancy, infancy or early childhood (to age 3).  Results include typical development, tips for parents, and information on nutrition, sleep, health and behavior.
 

OSF HealthSteps – Child Development
Part of HealthSteps Magazine provided by OSFHealthCare, this site lists typical developmental milestones through age 4 years.
 

Bright Futures Family Tip Sheets
Sponsored by the Bright Futures program of Georgetown University, the site provides 6-page tip sheets for Infancy, Early Childhood, Middle Childhood, and Adolescent.
 

Virtual Children's Hospital, Pediatric Growth & Development
Part of the University of Iowa’s Virtual Hospital, this site presents charts on physical growth for boys and girls from birth through age 18, developmental milestones/ language skills through age 5, and dental development through age 22.   Also provides links to other pediatric patient topics within the Virtual Children’s Hospital.