Intercom on Product Management - The ultimate resource for aspiring product managers
Nifty - Manage projects, work, and communications in one place.
Product School - The global leader in product management training
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
GitHub Project Management - No-fluff guide to building a collaborative development team
The Product Folks - A volunteer-led community of product managers and makers