The Product Manifesto - Product Managers face the biggest challenges of our day, which is why our community needs a common set of product principles.
The PM Interview - Practice PM Interview Questions (w/ timer).
Intercom on Product Management - The ultimate resource for aspiring product managers
Pramp for Product Managers - Practice product management mock interviews with other PMs
Product School - The global leader in product management training
Myskillwall - The best tool to prepare your job interview