Site Recommendation:
As I was doing some research this morning, I stumble on this site, Nemours: Kids Health, which has some basic helpful medical information.  There is a section for parents that includes very well written descriptions of a number of medical conditions and other material (some I'm sure you've seen before) nicely presented in an easy to read format.

http://kidshealth.org/parent/kh_misc/nemours.html#cat135