Uxcel - The easiest way to learn UX/UI design
Invision - Prototyping and collaboration for design teams
UX Challenges - Done reading about UX? Start doing it.
Marvel - Turn sketches, mockups and designs into web, iPhone, iOS, Android and Apple Watch app prototypes.
UI Coach - Become a better UI designer in 30 days
UXpin - Design is really about solving problems. UXPin is the UX Design Platform that gets that right.