Google's advanced search allows you to search by domain name (on bottom line of the advanced search form).
Entering .edu or .gov into this line will only return results from educational or US government sites, which tend to contain more reliable scholarly or factual information. You will still have to evaluate the sites for authority, accuracy, currency, and objectivity.
Issues of Geotimes, information on environmental geoscience and links to many good sites
Cornell University's interactive digital map of the world emphasizing geological and geophysical information
Land information for exploring our changing planet, including a map and photograph finder as well as a learning center for K-12 educators in biology, geology, hydrology and geography; and earthshots, satellite images of environmental changes
Access to geographical and GIS map resources
Links to online resources and lists of links in geology. Includes Resources for Earth Science Teaching
Gateway to an array of sites in all areas of geology, including regional geology, space science, geochemistry, gems, geological supplies, and much more
An earth science dictionary, satellite images, geologic time scale, a mineral identification chart and many other features. Includes an extensive section on Pennsylvania geology as well as geology for the rest of the United States
Searchable source of description and access information for over 15,000 Earth Science data sets
With many resources including Popular Links, Teacher's Resources and a Glossary
Annotated links to material about metamorphic rocks, migmatites and granitoid rocks, and related areas of "hard-rock" geology
ore than mineralogy and petrology, lists web resources in areas of interest to all geoscientists
information on solid-earth geophysics and glaciology
Links to sites, journals, directories and catalogs of interest to geoscientists
Connects researchers to the Survey's divisions of biological sciences, geology, mapping, and water resources. The U.S. Geological Survey Library has four main sections and is easily searchable. There is also a Science Topics section and for children, teachers and explorers, USGS and Science Education
Comprehensive collection of online courses that use the web to deliver geoscience content
Information on volcanology from the University of North Dakota