National Center for Health Statistics (CDC)
Your beginning place for health statistics. Many of the statistics are available at the national and state levels, and sometimes it is even more detailed--down to the county level.
Here are a few topics from this site: Diseases & Conditions (Asthma, Cholesterol, Diabetes, Heart Disease, Hypertension, Obesity); Health Care & Insurance (Ambulatory Care, ER Visits, Health Insurance Coverage, Hospital Use); Injuries; and Vital Statistics (Deaths, Births).