Plait

Virtual whiteboard for sketching hand-drawn like diagrams

Joplin - the privacy-focused note taking app with sync capabilities for Windows, macOS, Linux, Android and iOS.

draw.io is a JavaScript, client-side editor for general diagramming.

TagSpaces is an offline, open source, document manager with tagging support

A macOS app for customizing which browser to start

Ambient sounds for focus and calm.