Toolabs DSM - Design System Manager plugin for creating themeable designs
Now UI Kit - A beautiful Bootstrap 4 UI kit. Yours free.
Evie by unDraw - MIT licensed illustrations for your next project
Bots UI Kit - Fully customizable Sketch UI Kit for Messenger Platform
Haiku - Haiku is an open source OS catered specifically to the needs of personal computing.
Landing UI Kit - Handcrafted UI components for landing pages