Google Doctype is an open encyclopedia and reference library. Written by web developers, for web developers. It includes articles on web security, JavaScript DOM manipulation, CSS tips and tricks, and more. The reference section includes a growing library of test cases for checking cross-browser and cross-platform compatibility.
The Yahoo! User Interface Library is a set of utilities and controls, in JavaScript, for building richly interactive web applications using techniques such as DOM scripting, DHTML and AJAX. The YUI Library also includes several core CSS resources.
The OpenLaszlo platform allows developers to create applications with the rich user interface capabilities of desktop client software and the instantaneous no-download Web deployment of HTML.