Now UI Kit - A beautiful Bootstrap 4 UI kit. Yours free.
Diagrams for Mac - A diagram editor for visualizing structures and processes
UX Toolkit for Figma - Create beautiful user flow charts, sitemaps and wireframes
The Data Visualisation Catalogue - Reference tool for data visualisation
Landing UI Kit - Handcrafted UI components for landing pages
nivo - nivo provides a rich set of dataviz components