Jquery tools & jquery ui

jQuery Tools is a collection of the most important user-interface components for modern websites. Used by large sites all over the world.

http://flowplayer.org/tools/index.html

http://jqueryui.com/demos/

jQuery UI provides a comprehensive set of core interaction plugins, UI widgets and visual effects that use a jQuery-style, event-driven architecture and a focus on web standards, accessiblity, flexible styling, and user-friendly design. All plugins are tested for compatibility in IE 6.0+, FF 2+, Safari 3.1+, Opera 9.0+, and Google Chrome.