Chesapeake Energy Corp,the Oklahoma-based firm is the No. 1 driller in Ohio.
Rig Count Interactive Map by Baker Hughes, an energy services company.
Shale Sheet Fracking, a Youngstown Vindicator blog.
The Ohio Environmental Council, a statewide eco-group based in Columbus.
Earthjustice, a national eco-group.
People's Oil and Gas Collaborative-Ohio, a grass-roots group in Northeast Ohio.
Concerned Citizens of Medina County, a grass-roots group.
No Frack Ohio, a Columbus-based grass-roots group.
Fracking: Gas Drilling's Environmental Threat by ProPublica, an online journalism site.
Pipeline, blog from Pittsburgh Post-Gazette on Marcellus shale drilling.
Allegheny Front, environmental public radio for Western Pennsylvania.
Geisinger Health System, a non-profit chain of hospitals in eastern Pennsylvania, plans to use its datbase of patient records to determine whether natural gas drilling in the Marcellus shale in harming residents.
The hospital system began planning the project last year and started mining hundreds of thousands of records in recent weeks, Bloomberg News reported.
Geisinger is talking with foundations, the government and the gas industry to fund the expansion of the project.
"There's all these concerns about what the health risks are, but we're really limited to anecdotal data," said David Carey, director of Geisinger's Weis Center for Research.
The database can provide "real hard, rigorous scientific data," he said.
Recently, the Institute of Health, a branch of the National Academy of Sciences, said it would investigate the health threat from hydraulic fracturing or fracking.