PM Starter Pack - Practical guide on how to get started in product management
Product Resources List - The biggest list of free product management resources
Product School - The global leader in product management training
Product Wednesday - Every Wednesday, receive a handpicked selection of tools made for Product Managers, Product Designers, UX Researchers and every member of the Product team.
know/how Product Managers - A weekly newsletter with 5 practical tweet-length PM tips
Intercom on Product Management - The ultimate resource for aspiring product managers