I am a contractor for EPA and I help to coordinate the activities and services of EPA's 28 libraries across the country. Please visit our web site at http://www.epa.gov/natlibra/ .
There are organizations of environmental librarians. The one that I belong to is the Environment and Resource Management Division of the Special Libraries Association. The membership of this group consists of librarians that work in environmental libraries in government, industry, law firms, etc. If you'd like more information on ERMD, they have a web site at http://www.wco.com/~rteeter/ermd/ermd.html .
The American Library Association (ALA) also has a subsection for environmental librarians called the Task Force on the Environment. Their web site is at http://www.ala.org/alaorg/rtables/srrt/tfoe/ .
The Public Library Association, a division of ALA, would be a good organization to contact for information on public libraries. ALA and/or PLA publish directories of libraries across the country with addresses, phone numbers, the size of the population served, etc.
This forum is proving to be very interesting so far!
Lucy Park