Flinto - The prototyping tool designers have been waiting for.
The Product Management guide - A book on how to create and ship products that people love
Base UI Sketch Framework - Huge set of everything you need to design and prototype
Intercom on Product Management - The ultimate resource for aspiring product managers
Glyphy - Copy & paste fancy fonts + cool symbols ☞✺✐™
Xobin - Most Comprehesive Pre-Employment skills testing and Psychometric Assessment Platform.