Glimmer - Fast and light-weight UI components for the web
Element UI - A Desktop UI Library. Element, a Vue 2.0 based component library for developers, designers and product managers.
Preact.js - Preact is a fast 3kB alternative to React with the same modern API. Components & Virtual DOM.
GenesisUI - Bootstrap Admin Templates on steroids! Collection of premium bootstrap admin templates.
Svelte - Cybernetically enhanced web apps
Bootstrap - Simple and flexible HTML, CSS, and JS for popular UI components and interactions