Product School - The global leader in product management training
Invision - Prototyping and collaboration for design teams
Software Product Management Stack - Resources & tools to help you manage your software product
Marvel - Turn sketches, mockups and designs into web, iPhone, iOS, Android and Apple Watch app prototypes.
PM Starter Pack - Practical guide on how to get started in product management
UXpin - Design is really about solving problems. UXPin is the UX Design Platform that gets that right.