IRI/LDEO Climate Data Library - Climate-related datasets from the International Research Institute for Climate and Society at Columbia University
Marine Geoscience Data System (MGDS) - A data portal, hosted at the Lamont-Doherty Earth Observatory
(Columbia University), for a number of NSF-supported marine research programs
NASA Warehouse Inventory Search Tool (WIST) - Locate earth science data from NASA and affiliated centers
National Climatic Data Center (NCDC) - Meteorology and paleoclimatology
NCAR/UCAR Community Data Portal - Climate and weather datasets and visualization software from the National Center for Atmospheric Research and the University Corporation for Atmospheric Research
National Oceanographic Data Center (NODC) - World-wide marine environmental and ecosystem data
National Center for Atmospheric Research Computational & Information Systems Library
USGS National Satellite Land Remote Sensing Data Archive - Note that some data access is fee-based
GEON - Portal for datasets and visualization tools
National Snow and Ice Data Center (NSIDC) - Cryospheric datasets from ground field reseach and satellites
GenBank - is the NIH genetic sequence database, an annotated collection of all publicly available DNA sequences.
DigiMorph - Digital Morphology library is a dynamic archive of information on 3D scans, animations, and high-resolution X-ray computed tomography of biological specimens.
Dryad - Dryad is an international repository of data underlying peer-reviewed articles in the basic and applied biosciences. See their data submission page for instructions. Dryad posts two different Twitter feeds, one for general news about Dryad and open data (@datadryad), and one for notices of new data (@datadryadnew).
Biodiversity Heritage Library (BHL) is a consortium of natural history and botanical libraries that cooperate to digitize and make accessible the legacy literature of biodiversity held in their collections and to make that literature available for open access and responsible use as a part of a global “biodiversity commons.”
National Biological Information Infrastructure - This portal links to a wide variety of data sources, such as the Fisheries and Aquatic Resources Data Access Wizard and the Biogeographic Information and Observation System (BIOS). A full list of all data sets is available here
Protein DataBank - Experimentally determined structures for macromolecules (protein and nucleic acids). The site includes search and visualization tools
The Cell: An Image Library - Images of all cell types from all organisms, including intracellular structures and movies or animations demonstrating functions. This project relies upon the cell biology community to populate the library.
UniProt - Free protein sequences
Geodata.gov - One-stop for federal, state and local geographic data
GeoCommons.com GIS file repository and finding tool
Federal Geographic Data Committee - Provides access to the National Spatial Data Infrastructure (NSDI) Clearing House Network and the geodata.gov portal
National Geographic Data Center - Archive of datasets