http://faculty.vassar.edu/lowry/VassarStats.html
A very useful web site that gives guidance and does your statistics for you. No registration required.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi
The world’s biomedical literature searched for you at the touch of a button! No registration required.

See also: http://www.pubmedcentral.nih.gov/

http://www.who.int/topics/en/
The health topics section of the World Health Organization (WHO) web site.