Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
Figma Product Planner - Easiest way to plan, visualize, & share your product planing
Facebook Design - Resources for Designers from the Facebook Design team
InVision Studio - The world’s most powerful screen design tool
Taskade - Make lists, organize your thoughts, and be inspired to get things done. Taskade is a collaborative space for your tasks.
Design Principles - An open source repository of design principles and methods