jsPDF : A library to generate PDFs in client-side JavaScript.
Wave.js : Audio visualizer library for javascript. Create dynamic animations that react to an audio file or audio stream.
React : A JavaScript library for building user interfaces
Bespoke.js : Bespoke.js is a super minimal, modular presentation library for modern browsers, designed to foster a rich plugin ecosystem.
impress.js : It's a presentation framework based on the power of CSS3 transforms and transitions in modern browsers and inspired by the idea behind prezi.com
Add Clippy or his friends to any website for instant nostalgia.