Pico is an open source CMS application that is capable of very few things. It uses flat-files as the database and built with PHP. Simply, there is no setup and the app works instantly.
Chrome Logger is an extension that brings server-side code debugging to this tool. It has libraries for PHP, Python, Ruby, .NET, ColdFusion and Node.js. Also, new ones can be created with the documentation provided.
Koken is a free and self-hosted CMS (PHP-MySQL) that is focused on building websites where portfolio/gallery is in the core (like designer or photographer sites).