With all the discussion around other decent options for Content Management Systems, I'm surprised nobody has mentioned OctoberCMS (http://octobercms.com/) yet.

It's an awesome, highly extendable, very clean CMS to work with as a developer. Based on Laravel, it's also open source: https://github.com/octobercms/october

It gives you all the power of Laravel with some very nice features built in that make developing for it a breeze. Runtime extendable classes, event listeners, Twig templating, and an AJAX framework for interacting with the PHP side of your code are just a few of the features that it includes by default; not to mention the rapid development experience empowered by the Form & Lists widgets.

Disclaimer, I'm a maintainer on the project :)