Air Conditioning & Refrigeration Wholesalers (ARW )
http://www.arw.org/

Refrigeration Service Engineers Society (RSES)
http://www.rses.org/

Organizations:
Air-Conditioning, Heating & Refrigeration Institute (AHRI)
http://www.ahridirectory.org/

American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)
http://www.ashrae.org/

Consortium for Energy Efficiency (CEE)
http://www.cee1.org/

Heating, Airconditioning & Refrigeration Distributors International (HARDI)
http://www.hardinet.org/

Governmental Regulatory Bodies:
US Department of Energy (DOE)
http://www.doe.gov/

Energy Star
http://www.energystar.gov/

EPA Indoor Air Quality
http://www.epa.gov/iaq/

North American Technician Excellence (NATE)
http://www.natex.org/

Online Tools:
HVAC OP Cost
http://www.hvacopcost.com