Product School - The global leader in product management training
Product Snacks - Bite-sized learning cards for product managers
PM Starter Pack - Practical guide on how to get started in product management
Dash for Tumblr - Easiest way to learn to build Tumble themes
Software Product Management Stack - Resources & tools to help you manage your software product
know/how Product Managers - A weekly newsletter with 5 practical tweet-length PM tips