Lax.js - Create beautiful & smooth animations when you scroll
Invision - Prototyping and collaboration for design teams
ScrollMagic - The jQuery plugin for magical scroll interactions.
Marvel - Turn sketches, mockups and designs into web, iPhone, iOS, Android and Apple Watch app prototypes.
WOW.js - Animate elements on-scroll to catch attention. Such Magic.
UXpin - Design is really about solving problems. UXPin is the UX Design Platform that gets that right.