ASHRAE

American Society of Heating, Refrigerating and Air-Conditioning Engineers.

The foremost society for engineers in the HVAC/R field, the handbooks are worth the membership fee

Dan Holohan´s web site, he is probably the best source on the web for information on steam heat

SMACNA

Sheet Metal and Air Conditioning Contractors' National Association

The name tells you what they are!

RSES

Refrigeration Service Engineers Society

NATE

North American Technician Excellence

Working to get Technicians certified

ARI

National trade association representing manufacturers of more than 90 percent of North American produced central air-conditioning and commercial refrigeration equipment.

Charlie "Tec Daddy" Greer´s Website, Charlie is one of the leaders in teaching technicians how to increase sales to benefit themselves and the company