Reports, FAQ's and stats on many health conditions and issues.

A listing of various health datasets, interactive sites etc. from the U.S. Dept. of Health & Human Services.

This publication from the Centers for Disease Control is an annual (it comes out a little slowly - the current one online is for 2010) accumulation of statistics, not just on diseases, but on access to health care by ethnic group, income, and much much more.

National & state level stats on births, deaths, marriage, divorce as well as various surveys etc.

Excellent site for NY specific stats.

This and Tabers are the standard medical dictionaries.

Many links to hospital stats: scroll down for example to the HCUP Facts & Figures for an overall look at hospital stats - inpatient stays, stays by procedure etc.