http://www.epa.gov/OW/
The EPA's Office of Water. Contains information on publications, water laws and regulations, and other Websites that link to state water issues.
http://water.usgs.gov/
United States Geological Service. Good source of information on the water resources of the U.S.
http://www.worldwater.org/
The Pacific Institute for Studies in Development, Environment, and Security site contains data on world water resources and links to lots of other water-related sites.
http://www.cnie.org/NLE/CRS/
U.S. Congressional Research Service Reports on water. Click on "Water" in the left-hand frame.
http://www.worldbank.org/html/fpd/water/
The Water Supply and Sanitation Program at the World Bank offers many reports on economic aspects of water use in developing countries.
