Groups working on ecology and conservation of the Hudson River

• Hudson River Environmental Society
  (a non-advocacy group that holds meetings on a wide range of topics concerning the Hudson and its watershed)
  
  
• Hudson River Foundation
  (supports programs for research, education, and improvement projects on the Hudson)
  
  
• Hudson River Sloop Clearwater
  (lots of programs in ecological education and advocacy for protection of the Hudson, centered around a working Hudson River sloop)
  
  
• Scenic Hudson
  (an environmental organization and land trust working to protect, preserve and restore the Hudson River and its riverfront)
  
  
• The National Estuarine Research Reserve System:
  Hudson River Reserve, New York
  (A program of research and management on estuaries, including several on the Hudson)
  
  

State and federal agencies concerned with ecology of the Hudson

• New York State Department of Environmental Conservation Estuaries Program (New York State's major programs on the Hudson)
  
  
• United States Environmental Protection Agency
  (tons of useful information)
  
  
• United States Geological Survey
  (lots of useful information on water flows, biology, and contaminants)
  
  

Professional ecological societies

• American Society of Limnology and Oceanography
  (a group of people who study lakes, rivers, and the ocean for a living)
  
  
• Ecological Society of America
  (the major professional organization in America for ecological researchers and educators; good resources, links, and a job board)
  
  
• Estuarine Research Federation
  (the leading professional society for people who study estuaries)
  
  
• North American Benthological Society
  (a professional society for people interested in the stuff that lives at the bottom of streams, lakes, and wetlands; good resources, including photos, job board, and links)
  
  
• Society for Conservation Biology
  (the leading professional society in conservation biology)
  
  
• Society of Wetland Scientists
  (the group for people who work on wetlands)
  
  

Information about the Hudson

• Tide tables from NOAA
  
  
• Water flows and chemistry from the United States Geological Survey