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).