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.
The U.S. Geological Survey is taking a look at how drilling for natural gas can impact forests and other natural resources.
It is looking at how construction of well pads, roads and pipelines are impacting Bradford and Washington counties in Pennsylvania's Marcellus shale.
In Bradford County, 642 gas-extraction sites impacted 3,700 acres. That included 45 miles of new roads and 110 miles of new pipelines.
In Washington County, 949 gas-extraction sites resulted in 4,445 acres of disturbed land including 172 miles of new roads and 134 miles of new pipelines.
Click here to read more from The Marcellus Effect blog.