haçienda.io
Content should be distinct from presentation. You should be able to easily change the way your content looks without modifying it. Storing content as plain JSON achieves that.
Managing content should be clear and easy. Hacienda exposes a simple API based on HTTP verbs to create and modify your content.
Hacienda stores the content in a local Git repo enabling easy access to history of changes.
ThoughtWorks uses Hacienda to store most of its editable content. Their corporate website, thoughtworks.com, is a medium sized website with 200k monthly views and lots of the content on the website: client stories, news, events, profiles, and more are all back-ended by Hacienda.
A very long while back the website was built using Drupal. This had lots of drawbacks, from difficulty to test, to clunky user experience for editors. The revamp of the website enabled the team to experiment in building an alternative to big CMSs like Drupal. Hacienda is part of the system that was born as a result.