Some of my favorites:
We're a distributed, remote-only company where people work remote without missing out. For this, we use asynchronous communication and are as open as we can be by communicating through public issues, chat channels, and placing an emphasis on ensuring that conclusions of offline conversations are written down. https://about.gitlab.com/handbook/#communication
Don't frown on people taking time off, but rather encourage that people take care of themselves and others. https://about.gitlab.com/handbook/#paid-time-off
Runbooks for the on-call person for common issues https://gitlab.com/gitlab-com/runbooks
Edit: Link formatting