Another great thing about jQuery is that it's extremely lightweight, so it will not bog down your website's load times. The jQuery portal also provides many useful tutorials on how to get started using this powerful tool. You can download jQuery source from this link: http://jquery.com/.
2) DoJo ToolKit 1.8
Dojo Toolkit can be downloaded at: http://dojotoolkit.org/download/.
3) YUI Library
YUI is an open-source Javscript library that helps to build rich, interactive websites. Like JQuery, YUI manipulates DOM elements to apply visual effects such as transition. Built by the engineers at Yahoo! in 2005, YUI was then released for public use. Using YUI is as easy as a,b,c,d ! Developers just have to include the line “<scriptsrc="http://yui.yahooapis.com/3.6.0/build/yui/yui-min.js"></script>>” in their HTML page, and they will be able to load any YUI components in the page.
YUI has an impressive community of users, and these resources are aggregated in the following page :http://yuilibrary.com/community/. YUI is a must-try for aspiring web developers and veterans alike. Download YUI Library at this link: http://yuilibrary.com/yui/quick-start/.