iOS Design Kit - The newest library of native iOS templates
Elements for Sketch - High-quality UI Kits in Sketch, for free
iOS 12 GUI - Free collection of UI components and screens of iOS 12
Tailwind CSS - A utility-first CSS framework for rapidly building custom user interfaces.
Ionic Sketch UI Kit - Smart Sketch library for Ionic 3
DynaMaker - Cloud service for Visual Product Configuration with parametric geometry and CAD / BIM