Is a dangerous pipeline running through your community? Journalists searching for stories may get some limited help from the National Pipeline Mapping System (NPMS). Though deliberately hobbled, it can yield some useful information at a local scale.
Before 9/11, the NPMS was online and searchable — its only drawback being inaccurate and out-of-date data. It was the principal tool by which both the public and the Pipeline and Hazardous Materials Safety Administration could track pipelines that could present hazards to communities. Like many other environmental infrastructure databases, the NPMS was taken down after 9/11, ostensibly to protect the public from terrorist attacks — but also conveniently protecting the pipeline companies and PHMSA from oversight and accountability.
Historically, faulty pipelines have consistently presented a far more lethal threat to U.S. residents than terrorists. After a gas transmission line explosion killed 12 near Carlsbad, NM, in August 2000, journalists Jeff Nesmith and Ralph Haurwitz did a landmark investigative series exposing U.S. neglect of pipeline safety that ran in the Austin Statesman-American in July 2001. Congress responded with Pipeline Safety Act amendments in 2002. But, perhaps because of rampant secrecy in the name of "homeland security," few journalists for the next decade investigated whether the federal government was enforcing safety rules. It was not until the devastating pipeline explosion of 2010 killed eight and leveled 35 homes that pipeline safety returned to the agenda of U.S. journalism.
Today after a decade of neglect, the NPMS is partly back online and marginally functional. You can only search and view maps at the level of individual counties (a feature possibly meant to deter terrorists and journalists alike). The information is not necessarily complete or accurate. Parts of the NPMS site simply do not work, for reasons unknown. But if you want to get a general clue about the location of major natural gas and hazardous liquid pipelines in your community, the NPMS is one place to start.
Of course, if you are serious about pipeline safety you will want to pay for a commercial map or data product — not the one used by the PHMSA regulators. Pennwell, the company that publishes Oil & Gas Journal, publishes an excellent set of state-by-state maps.  Rextag, a Hart Energy company, publishes a comprehensive geotagged data set.  These are available to the public.
The search page for the NPMS is here. 
Oh, and if you want the national pipeline overview map that PHMSA is denying you, you can get it from the Energy Information Administration. 
Another reliable and independent source of information is the Pipeline Safety Trust.  Their site offers help using the NPMS.