Kirby is a file-based CMS, which is very easy to setup and use and yet very flexible.
The core of the Kirby CMS and Zootool is my Kirby Toolkit. It's a handy collection of PHP methods that make your life as a PHP developer easier. It's open-source.
A simple PHP Gantt Class
A simple form submission handler for PHP
PHP Browser Selector
A newer version of that code can be found in kirby, so you should check out that instead.
I'm always playing around with new stuff and techniques and so one day I decided to build Things for Mac (which is a great app by the way) with HTML 5 and CSS3. It does not make sense at all, but it's good to see what's possible with a webkit browser and some simple web techniques.