Responsive Viewer - View multiple screen dimensions in one view
Design Principles - An open source repository of design principles and methods
Responsinator - Designed to test responsive websites on different devices.
UX Research Field Guide - Your map to the world of UX research 🌏🕵️♀️
Multi Screen Test - Test your site at different screen resolutions & devices.
Business-Driven Digital Product Design - A guide on how to create influential user experience