On-line Data Portals:

U.S. Geological Survey (USGS) EarthExplorer (EE)
Commercial imagery, such as IKONOS, QuickBird, OrbView, and the Advanced Wide Field Sensor (AWiFS); registration required — EE also includes aerial photos, elevation data and satellite data available through the USGS

USGS Hazards Data Distribution System (HDDS)
Remote sensing and cartographic data acquired for various hazards events

U.S. Department of Agriculture (USDA) Geospatial Data Gateway
Natural resources and environmental data, such as orthoimagery, and hydrologic, soils and cartographic data

USGS Geospatial One-Stop (GOS)
Existing imagery or planned data acquisitions for Federal agencies

Web-based Access and Retrieval Portal (WARP)
Commercial high-resolution imagery, such as IKONOS, QuickBird, and OrbView; registration required

Digital Globe ImageFinder
DigitalGlobe archive of QuickBird imagery

GeoEye GeoFUSE
GeoEye IKONOS and OrbView imagery as well as IRS Resourcesat-1 imagery; registration required

Shapefile/KML Coverages:

USGS Commercial Data Purchases (UCDP) Delimited Text file, KML file and Shapefile
Commercial imagery holdings available through the USGS, such as IKONOS, OrbView, QuickBird, and AWiFS

GeoEye, OrbView-3 Panchromatic (Pan), Multispectral (MS), IKONOS holdings