American Council on Exercise (ACE)
ACE has more than 45,000 active instructors currently working. They offer certification in the following areas: Personal Trainer, Group Fitness Instructor, Lifestyle & Weight Management Consultant, and Clinical Exercise Specialist. Look here for information on local trainers and facilities.

Aerobics and Fitness Association of America (AFAA)
AFAA has certified more than 150,000 instructors since 1983. They offer continuing education and preparation for certification and information on locating instructors in your area as well as facilities.

American College of Sports Medicine (ACSM)
ACSM's goal is to integrate new science and information into the world of fitness.