Have you heard of ChallengeLoop? http://www.challengeloop.com. ChallengeLoop allows you to motivate your clients to achieve their fitness goals and track their progress along the way. It is both an iPhone app and website.
The Training Notebook app is pretty good. you can take photos of clients to track progress, set-up new clients, and create custom programs for clients. It was built by a personal trainer for other trainers.
There’s also an online version for tracking lots of clients from a desktop/laptop.
The answers to these past questions might help.