KeystoneJS - Open source framework for developing database-driven websites, applications and APIs in Node.js.
HashBrown CMS - A truly different approach to content management. Instead of being on-site, HashBrown publishes content to your website remotely, so you can build them using whatever language or framework you prefer.
Contentflow - Live Streaming Software
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.