Now UI Kit - A beautiful Bootstrap 4 UI kit. Yours free.
Maze - Beautiful & actionable analytics for InVision prototypes
UX Toolkit for Figma - Create beautiful user flow charts, sitemaps and wireframes
Dimensions Toolkit - Chrome Extension for designers to test responsive websites.
Landing UI Kit - Handcrafted UI components for landing pages
ProtoPie - ProtoPie is the easiest tool used to turn your UI/UX design ideas into highly interactive prototypes for mobile, desktop, web, all the way to IoT.