Abstract - A secure, version-controlled hub for your design files
Invision - Prototyping and collaboration for design teams
Kactus - Design version control without changing your tools
Marvel - Turn sketches, mockups and designs into web, iPhone, iOS, Android and Apple Watch app prototypes.
Git Sketch Plugin - Version control for designers
UXpin - Design is really about solving problems. UXPin is the UX Design Platform that gets that right.