Research Labs @ GMP

Repository for most US supported data/research. USGS is one of the participating members.

TIGER (Topologically Integrated Geographic Encoding and Referencing) products are spatial extracts from the Census Bureau's MAF/TIGER database, containing features such as roads, railroads, rivers, as well as legal and statistical geographic areas.

The Chronic Disease GIS exchange is an on-line forum for public health professionals and community leaders to learn and share techniques for using GIS to enhance chronic disease prevention and treatment

Here are some places to find/access publicly available data.