Lunr.js
A bit like Solr, but much smaller and not as bright
Batman
Fighting Crime and Kicking Apps
Lozad.js
🔥 Highly performant, light ~0.9kb and configurable lazy loader in pure JS with no dependencies for responsive images, iframes and more
Pagerjs
The Single Page Application Framework for KnockoutJS
Page.js
Micro client-side router inspired by the Express router (~1200 bytes)
Bacon.js
FRP (functional reactive programming) library for Javascript
RequireJS
A file and module loader for JavaScript
Tangle
a JavaScript library for reactive documents
JS Signals
Custom Event/Messaging system for JavaScript inspired by AS3-Signals
History.js
History.js gracefully supports the HTML5 History/State APIs (pushState, replaceState, onPopState) in all browsers. Including continued support for data, titles, replaceState. Supports jQuery, MooTools and Prototype. For HTML5 browsers this means that you can modify the URL directly, without needing to use hashes anymore. For HTML4 browsers it will revert back to using the old onhashchange functionality.
Framework7
Full Featured HTML Framework For Building iOS & Android Apps
Durandal
A cross-device, cross-platform client framework written in JavaScript and designed to make building Single Page Applications (SPAs) easy to create and maintain.
Visibility.js
Visibility.js allows you to determine whether your web page is visible to a user, is hidden in background tab or is prerendering. It allows you to use the page visibility state in JavaScript logic and improve browser performance by disabling unnecessary timers and AJAX requests, or improve user interface experience (for example, by stopping video playback or slideshow when user switches to another browser tab).
Tock
Timer Object/Class. Kickass!
Supermodel
Supermodel - Minimal Model Tracking for Backbonejs
Mustache.js
Minimal templating with {{mustaches}} in JavaScript
Modernizr
Modernizr is a JavaScript library that detects HTML5 and CSS3 features in the user’s browser.