Now UI Kit - A beautiful Bootstrap 4 UI kit. Yours free.
Dimensions Toolkit - Chrome Extension for designers to test responsive websites.
UX Toolkit for Figma - Create beautiful user flow charts, sitemaps and wireframes
One Click Test - Tool for quickly testing your design layout in one click.
Landing UI Kit - Handcrafted UI components for landing pages
Flexbox Grid - Grid based on CSS3 flexbox