AldoContent is a lightweight CMS focused on usability and simplicity. It is designed for multilingual Web sites and can have sections with public and private content. It has file management, is extensible with plugins, and uses gettext for localization. Is written in PHP for a MySQL backend.
Molinos CMS is a modular CMS. It supports multiple Web sites per installation, multiple domains per Web site, and different subdomains for different Web site sections. It uses XSLT for templating; templates can be organized in themes, which can be applied to either all pages or particular pages. It can use MySQL or SQLite for data stoarge; all data is available in XML format, ready to use by templates and scripts. User groups (roles) and advanced ACL can be used to control access to that data. It supports many caching and code optimization techniques. Data storage is optimized to minimize queries required to display pages. There are modules for integrating with various third-party services (over 70 modules). Modules are simple to write using the provided documentation (currently only available in Russian). Web sites can use local and system modules simultaneously. It works with most Web servers, and has a built-in Web server (for localhost development). It also has a CLI for most tasks.
AlphaLemon CMS is a content management system built on top of the Symfony2 framework. It is designed to make it as easy as possibile to manage a Web site without requiring programming or a large learning curve, while giving developers a robust and flexible framework on which to build Web applications and distributable extensions.
MockMockWeb is a Heroku-ready Node.js-based Web application server which allows you to mock up a website in seconds. It allows you to instantly launch a website which sends an empty page (with status 200) to any request/URL and edit any page on the spot. You can also edit the layout shared throughout your website. It lets you build a mock (sometimes real) website in a request-driven interaction.
papaya CMS is a Web Content Management System based on open standards (including XML, XSLT, PHP, and MySQL/PostgreSQL). It is compatible with almost every operating system, is platform-independent, is multi-lingual, offers great usability, and is easy to extend via its plugin system. It is scalable and perfect for business websites.
Chyrp is a blogging engine designed to be very lightweight while retaining functionality. It has powerful theme and extension engines, so you can personalize it however you want. The code is well-documented, and it has a very strong structure that's loosely based on the MVC design pattern. Chyrp allows importation from several different blogging engines and uses a system called "feathers", which are basically templates for custom posts.
phpsqlitesite is a minimal PHP/SQLite content Website system. It gives you a searchable multilingual site with automatic navigation and optional social sharing and comment sections. It consists of one PHP source code file and one SQLite database file, with no requirements other than PHP and SQLite.