Easy Testimonial PHP Software
This is just a copy - paste code to include testimonials on any website.
This script uses file storage, but I recommend hooking it up to a mySQL if you have enougth time, but you can stick to file storage if you're comfortable with it.
You can find the demo here : http://easy-development.com/testimonial_demo/
This script uses Twitter Bootstrap.
This isn't a "master piece" testimonial software, but it's something basic you can adapt for your needs.