Biosolids:
Mid-Atlantic Biosolids Association
Cornell Waste Management Institute
PA DEP Biosolids site
US EPA Biosolids site

Composting:
Professional Recyclers of Pennsylvania (PROP)
U.S. Composting Council
Penn State Organic Materials Processing & Education Center
PA DEP Composting site
US EPA Composting site
Cornell Composting

Composting Training and Certification:
Professional Recyclers of Pennsylvania (PROP)

Compost Testing:
Penn State Ag Analytical Services Lab
Solvita
Control Labs
Woods End Labs
US Composting Council Seal of Testing Assurance (STA) program

Brownfields Restoration:
USEPA Brownfield page
PA DEP Land Recycling Program
National Brownfields Association