Invision - Prototyping and collaboration for design teams
The Product Management guide - A book on how to create and ship products that people love
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
Intercom on Product Management - The ultimate resource for aspiring product managers
Craftwork - A collection of User Interface resources made by Craftwork
Software Product Management Stack - Resources & tools to help you manage your software product