http://www.osha.gov/Publications/osha3154.pdf
http://www.osha.gov/Publications/osha3155.pdf

OSHA's four heat stress information cards: The Heat Equation, Heat Exhaustion, Heat Stroke - A Medical Emergency, How to Protect Workers. Intended to be printed and placed in the workplace. In PDF, requiring Adobe Acrobat. First link in english, second in Spanish.