Andrés Ruzo of the SMU Geothermal Lab prepared a guide titled Questions to Consider Before Starting a Geothermal Venture. It includes a list of companies and government agencies with their contact information.
Data on oil/gas well temperatures are available through the National Geothermal Data System (NGDS) and on the SMU Node of the system there are over 30,000 sites across the central and eastern US and off-shore Gulf Coast.
The report The Future of Geothermal Energy: Impact of Enhanced Geothermal Systems (EGS) on the United States in the 21st Century contains many useful tables and graphs. Figure 7.3 has been used as a basis for a chart the SMU Geothermal Lab has created showing the amount of energy you can produce from different combinations of fluid flow rates and temperatures.
The OpenEI website contains many links including to Geothermal Data, Permitting and Policy, and Geothermal Financing.
A dictionary of oil/gas terminology is available through Schlumberger's website.