The National Federation of Professional Trainers (NFPT) is a good certification.
Another is the National Gym Association (NGA).
I am a NFTP Certified Personal Trainer. I am also a NGA Certified Personal Trainer and a NGA Master Fitness Trainer.
My certifications are well respected at the Birmingham, Alabama YMCA, where I am a full-time Personal Trainer.
I am the NGA Chairman for the State of Alabama and as such, can offer candidates the NGA Personal Trainer Certification Course for $300, a savings of $50 off the NGA web site price. PM me if up are interested or email me at firstname.lastname@example.org and I will answer your questions.
Regards, Old Navy