International Geothermal Association
Information on geothermal energy in use around the world, world conferences on geothermal, and links to related web sites.
http://iga.igg.cnr.it/index.php

Southern Methodist University Geothermal Lab
Information about heat flow, temperature logging, geothermal resource assessments, and education.
http://www.smu.edu/geothermal/

Energy Commission Geothermal Program
Geothermal Energy in California
http://www.energy.ca.gov/geothermal

New Zealand Geothermal Association
Purposes include encouraging research, development and use of geothermal energy in New Zealand.
http://www.nzgeothermal.org.nz/

GeoEnergy Solutions Inc.
Provides design and installation of geothermal heating and cooling systems. Also offers sonic drilling for geothermal systems. Based in Bolton, Ontario.
http://www.geoenergy-solutions.com/

European Geothermal Energy Council (EGEC)
Promotes geothermal energy research and development. Includes news, events, details on joining and board of directors.
http://www.egec.net/

Wikipedia: Geothermal Power
Free encyclopedia article describing the concept of geothermal power. Addresses technical aspects, type of sources, electrical generation and cost.
http://en.wikipedia.org/wiki/Geothermal

DOE: Geothermal Energy
Idaho National Laboratory
http://geothermal.id.doe.gov/

Geothermal Energy Technology (GET)
The Geothermal Technologies Legacy Collection provides searchable access to Department of Energy sponsored full-text reports, historic and current.
http://www.osti.gov/get/gethome.html

Hydron Geothermal Systems
Design, consulting and sales of geothermal systems using stainless steel heat pumps . Projects include residential, industrial and commercial applications. Service area includes Michigan, Indiana and Ohio.
http://www.hydrongeo.com/