The idea behind Rainyday.js is to create a JavaScript library that makes use of the HTML5 canvas to render an animation of raindrops falling on a glass surface. Rainyday.js features extendable API, collision detection and is easy to extend with your own implementations of different animation components. It is a pure JavaScript library which uses HTML5 features so it’s supported by most of the modern browsers. It is licensed under GNU GPL license.
Requirements: JavaScript Framework
Demo: http://maroslaw.github.io/rainyday.js/
License: GPL License