Overview:

The chief deposits of "dry gas" (not associated with oil) are in Texas, Louisiana, Kansas, Oklahoma, Kentucky and West Virginia. Considering both "wet" and "dry" gas, the leading states are Texas, California, West Virginia, Louisiana, Kansas, Oklahoma, Pennsylvania, Kentucky and Ohio. Many other states have relatively large scattered supplies. So-called "proved reserves" in the US are around 160 trillion cubic feet of gas.

As with oil, finding gas is the job principally of geologists and many of the same techniques are used, especially seismic studies. In fact, the discovery of gas is often a byproduct of the search for oil.

Trade Associations:

American Association of Petroleum Geologists.
January 2000 update: This URL was not working during this update.
Masera AAPG-Data Systems (GEOBYTE-DOM)
1743 East 71st St.
Tulsa, OK 74136-5108
European Association of Geoscientists & Engineers.
Geological Association of Canada.
Geological Society of America.
Society of Independent Professional Earth Scientists - for the consulting earth scientist.

Yahoo Sites:

Science: Earth Sciences: Geology and Geophysics.
Business and Economy: Companies: Scientific: Geology and Geophysics..
Science: Earth Sciences: Geology and Geophysics: Exploration Geophysics.
Computers and Internet: Software: Scientific: Geology and Geophysics.

Government information:

Energy Information Administration (home page)
US Geologogical Survey provides maps, research reports and educational materials.

Trade periodicals and publications:

PennWell has books, maps of gas fields, directories and databases.

Other sources:

Geological Society of America has numerous publications as well as web resources.
Energy Research Clearing House is an organization be created to promote collaborative exploration and production research.

Sample gas exploration firms:

Alberta Energy Company - oil and gas exploration and production company.
Anadarko Petroleum Corporation - services for oil and gas exploration and development.
Arcis Corporation - seismic services for the exploration needs of the oil and gas industry.
Arrowhead Minerals Corp. - junior resource company exploring for oil and gas.
Bellwether Exploration Company - independent oil and gas company engaged in the acquisition, development, exploration, and production of oil and gas properties.
Brigham Oil & Gas L.P. - oil and gas exploration and development company focusing on the implementation of 3D seismic techniques.
Cedyco Corporation - aquisition, exploration, development and production of oil and gas for the Gulf Coast Region. -- January 2000 update: This URL was not working during this update.
Cedyco Corporation (CEDYCO-DOM)
P.O. Box 27528
Houston, TX 77227
US
FX Energy - explores for oil and gas primarily in Poland and the western United States and produces oil from fields in Montana and Nevada.
Gibraltar Energy - exploration and production company, operating primarily in the Black Warrior Basin of Mississippi.
Harken Energy Corporation - explores for, develops and produces oil and gas reserves domestically and internationally.
Hilton Petroleum - exploration, development and production of onshore oil and natural gas in North America.
International Rochester Energy Corp. - Canadian based international oil and gas exploration company.
InTerraActive - specializing in prospects ignored by larger companies because of urban location.
Laser Exploration, Inc - technology that detects oil and gas deposits onshore and offshore.
Marienfeld Royalty Corporation - Buyer of minerals and royalties from income producing oil and gas properties located in the United States and Canada.
OMNI Energy Services - diversified support company that provides an integrated range of services to geophysical and exploration and production companies engaged in the acquisition of 3D on-shore seismic data.
Nu-Sky Energy, Inc. - a public oil and gas company engaged in the acquisition and development of petroleum and natural gas in Western Canada.
Petrophysics, Inc. - specializing in relating geological information from well logs to seismic data. Developing advanced synthetic seismogram technology.
PetroStar - provides a land based deep well workover service supplying rigs, extra equipment, trained crews, and living quarters.
Pinnacle Oil International Inc. - oil and gas exploration company with exclusive rights to the Stress Field Detector (SFD).
Santa Fe International Corporation - international offshore and land contract driller. Santa Fe owns and operates a fleet of 54 marine and land drilling rigs.
Technical Drilling Services, Inc. - author mud logging software as well as a provider of mud logging services.
Techstar Exploration January 2000 update: This URL was not working during this update. (temporarily unavailable) - devoping oil and gas prospects for the industry.
Texas Meridian Resources Corporation - independent oil and natural gas exploration company.
Tidelands Geophysical Co. - seismic data gathering and petroleum exploration.
WestCastle Energy Trust - oil and gas property acquisition trust providing management on operations, development and finance. January 2000 update: This URL was not working during this update.
Westcastle Energy Trust Ltd. (WESTCASTLE-DOM)
3100 350 7th Avenue S.W.
Calgary, Alberta T2P 3N9
CA
WhitMar Exploration - maintaining an inventory of oil and gas exploration prospects for qualified investors.
Zavanna, LLC - high-tech oil and gas exploration and development company based actively exploring in 8 US and 2 Canadian basins.