Product Resources List - The biggest list of free product management resources
SaaS CSS - Design inspiration for SaaS specific web products
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.
Muzli - UI/UX and Design Inspiration Chrome Extension
Intercom on Product Management - The ultimate resource for aspiring product managers
UI Movement - The best UI design inspiration, daily