A collection of more than "20,000 descriptions of Earth science data sets and services covering all aspects of Earth and environmental sciences." Specific topic areas include:

• Agriculture
• Atmosphere
• Biological Classification
• Biosphere
• Climate Indicators
• Cryosphere
• Human Dimensions
• Land Surface
• Oceans
• Paleoclimate
• Solid Earth
• Spectral/Engineering
• Sun-Earth Interactions
• Terrestrial Hydrosphere

From NASA's Goddard Space Flight Center.