While much GIS data can now be found online through a common internet search engine, the sites listed below are dependable, trustworthy sources of high-quality GIS data
Maine Office of GIS Data Catalog: GIS Data for the state of Maine; primarily vector data but also some tables are raster datasets
Digital Atlas: Teaching tool available to all members of the University of Southern Maine community. Building on data from MEGIS and others, it was compiled and developed by USM Geographic Information Systems through the efforts of Matthew Bampton, Matthew Cadwallader, Jay Desmond, Sean Neely, and Michele Tranes.
MEDOT CORS Data: Locations of CORS (Continuously Operating Reference Stations) in Maine.
Osher Map Library collection Search: Inventory of Online Resources from the Osher Map Library
Maine Department of Environmental Protection: Access to Maine DEP GIS data. It is a mix of Google Earth and Shapefile formats.
GOS - Geospatial One Stop: Federal, State, and Local geographic data on a wide variety of topics
The National Map Small-Scale Collection (formerly National Atlas): Vector, raster, and tabular data for the United States on a wide variety of topics
Geospatial Data Gateway: Elevation, imagery, soils data, and climate data for the United States
The National Map Download Viewer: Elevation, land cover, and other GIS data for the United States
NOAA NGS CORS: National Locations of CORS
United Nations Environment Programme Global Environment Outlook (GEO) Data Portal: Vector and Raster data at the national, regional, and global scales
USGS Global Visualization Viewer: Landsat, ASTER, MODIS data among others; a reproduction fee is required for some datasets
USGS Earth Explorer: Satellite imagery and aerial photography, including Hyperion and ALI; a reproduction fee is required for some datasets
GLCF: Global Land Cover Facility: Satellite imagery and products derived from satellite imagery, e.g. Landsat, ASTER, etc.