Invision - Prototyping and collaboration for design teams
The Product Management guide - A book on how to create and ship products that people love
Marvel - Turn sketches, mockups and designs into web, iPhone, iOS, Android and Apple Watch app prototypes.
Product School - The global leader in product management training
UXpin - Design is really about solving problems. UXPin is the UX Design Platform that gets that right.
Product Management Exercises - A repository of product manager job interview exercises