Inferno - An extremely fast React-like javascript library for building modern user interfaces.
Vue.js - Reactive Components for Modern Web Interfaces
Preact.js - Preact is a fast 3kB alternative to React with the same modern API. Components & Virtual DOM.
Webix UI - An enterprise JavaScript Library for cross-platform app development with HTML5 JavaScript widgets and easy integration with most popular JavaScript Frameworks.
w2ui - W2UI is a small JavaScript UI library with a complete set of widgets: layout, grid, sidebar, toolbar, tabs, fields, popup, utilities.
Polymer - Polymer is a library that uses the latest web technologies to let you create custom HTML elements.