ACSM "promotes and integrates scientific research, education, and practical applications of sports medicine and exercise science to maintain and enhance physical performance, fitness, health, and quality of life."
The NSCA focuses on the practical application of research to improve athletic performance. Look under Education for some free resources, including articles, videos and podcasts. Much more information is available to members.
An organization committed to the advancement of exercise physiologists, ASEP also publishes the Journal of Exercise Physiology Online and Professionalization of Exercise Physiology Online - both peer-reviewed journals.
These sites are good sources for facts, figures, and other data on health-related issues.