enduro.js - Code-only, no-clicking, flat-file, node.js cms for professionals. With everything needed - Sass, iconfont generator, spritesheet generator, templates...
Contentflow - Live Streaming Software
KeystoneJS - Open source framework for developing database-driven websites, applications and APIs in Node.js.
Ghost - Ghost is a fully open source, adaptable platform for building and running a modern online publication. We power blogs, magazines and journalists from Zappos to Sky News.
Markdown by DaringFireball - Text-to-HTML conversion tool/syntax for web writers, by John Gruber
WordPress - WordPress is web software you can use to create a beautiful website or blog. We like to say that WordPress is both free and priceless at the same time.