Common Childhood Illnesses/Viruses:
http://www.cdc.gov/parvovirusB19/index.html
This is a fabulous website that has information for parents, kids and teens. It covers various illness and infections, general health, skin rashes, etc. There is a wealth of information here.
http://kidshealth.org
To list a few:
http://kidshealth.org/parent/infections/skin/hfm.html
http://kidshealth.org/parent/infections/lung/strep_throat.html
http://kidshealth.org/parent/infections/fungal/ringworm.html
http://kidshealth.org/parent/infections/eye/conjunctivitis.html
http://kidshealth.org/parent/infections/skin/eczema_atopic_dermatitis.html
http://kidshealth.org/parent/infections/skin/scabies.html
http://kidshealth.org/parent/infections/skin/chicken_pox.html