Earthdata Search
NASA's Earthdata Search (formerly Reverb) allows you to search, discover, visualize, refine, and access NASA Earth Observation data.
Remote sensing
USGS Data Pool
The Data Pool is the publicly available portion of the Land Processes Distributed Active Archive Center online holdings.It offers ASTER data covering the US and its territories and global MODIS data. It offers FTP access to selected data products. All data are available at no cost.
Global Data Explorer (GDEx)
The GDEx data access interface is the result of collaboration between the Land Processes Distributed Active Archive Center and George Mason University's Center for Spatial Information Science and Systems.
USGS Global Visualization Viewer (GloVis)
GloVis is an online search and order tool for selected satellite and aerial data. Through a graphic map display, the user can select any area of interest and immediately view all available images within the USGS inventory for the specified location.
USGS EarthExplorer
EarthExplorer provides online search, browse display, metadata export, and data download for earth science data from the archives of the USGS.
Govt of Canada Geospatial Data
The Government of Canada Geospatial Data Extraction Tool (formerly GeoGratis) provides free access to geospatial data and maps published by Natural Resources Canada.