I'm keeping all my notes under source control in GitHub:

* notes from literature I read (articles, books, forums).

* code templates for easy starting of new projects.

* docker with tools I constantly use (including the window manager) - that way I can always have my setup anywhere on any OS.

* passwords (encrypted with YubiKey HW tokens + PIN via rage).

* interviews for candidates for our team.

* vacation destinations.

* ideeas for presents.