DOMAssistant : The modular lightweight JavaScript library, with CSS selectors, event handling, AJAX and complete Unicode support
Prototype : Easy Ajax and DOM manipulation for dynamic web applications
Autotrack : Automatic and enhanced Google Analytics tracking for common user interactions on the web.
css3-mediaqueries-js : make CSS3 Media Queries work in all browsers (JavaScript library)
clipboard.js : Copy text to the clipboard shouldn't be hard. It shouldn't require dozens of steps to configure or hundreds of KBs to load. But most of all, it should...
Add Clippy or his friends to any website for instant nostalgia.