React Native Desktop - Build OS X desktop apps using React Native
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.
Arbiter IDE - The offline-friendly, in-browser IDE for pure JS prototypes
SnipNotes - SnipNotes is your clever notebook for iPhone, iPad, Mac and Apple Watch.
CodeOnline - A remote and secure workspace powered by VSCode
Trilium Notes - Trilium Notes is a hierarchical note taking application.