Use to track funding expended on lobbying by trade associations, manufacturing groups, and individual companies.
Experts, CEO's, and other influential people testify before Congress on any given subject. You can track influence by seeing who testified and which business or organization they are affiliated with.
Use Proquest Congressional to see if one of these organizations testified at a hearing on your topic
Environmental Defense Fund (PAC is called Environmental Defense Action Fund) http://www.edf.org/home.cfm
Nature Conservancy http://www.nature.org/
Earthjustice Legal Defense Fund http://www.earthjustice.org/
Natural Resources Defense Council www.nrdc.org/