Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
SnipNotes - SnipNotes is your clever notebook for iPhone, iPad, Mac and Apple Watch.
Invision - Prototyping and collaboration for design teams
Trilium Notes - Trilium Notes is a hierarchical note taking application.
Sketch - Professional digital design for Mac.