Collect, test, and experiment with interface pattern pairings of CSS & HTML. Pears is an open source WordPress theme, enabling people like you to get your own pattern library up and running quickly.

Presentation framework based on CSS3 transforms and transitions.

Bootstrap is a toolkit from Twitter designed to kickstart development of webapps and sites.
It includes base CSS and HTML for typography, forms, buttons, tables, grids, navigation, and more.

Processing.js is an open programming language for people who want to program images, animation, and interactions for the web without using Flash or Java applets. Processing.js uses Javascript to draw shapes and manipulate images on the HTML5 Canvas element. The code is light-weight, simple to learn and makes an ideal tool for visualizing data, creating user-interfaces and developing web-based games.

Processing.js is explicitly developed for browsers that support the HTML5