Environmental Statistics & Research: US National

Climate

GlobalChange.gov
Includes data, resources, and multimedia related to climate change, along with the current National Climate Assessment.
United States Daily Weather Maps Project
Historical daily weather maps from 1871 thru 2002 and a link to more recent daily weather maps.
El Niño Page (National Oceanic and Atmospheric Administration)
National Climatic Data Center (National Oceanic and Atmospheric Administration)

Land

Bureau of Land Management
United States Geological Survey
Focuses on Ecosystems, Geology, and Climate and Land Use

Species

Endangered Species Program
Includes  information on threatened and endangered animals and plants. See also the local offices of the U.S. Fish & Wildlife Services.

Water

Water Resources of the United States
Includes the Water Data for the Nation, which provides access to years of historical and real-time water data collected by the U. S. Geological Survey.

General

Science Inventory
A searchable database of Environmental Protection Agency science activities and scientific/technical work products.
Science.gov
A gateway to authoritative selected science information provided by U.S. Government agencies, including research and development results.