Accordion for Ext JS Library
There is the fully featured example on the Live Demo Page with various types of Accordions (left pane, embedded, resizable, in popup) and various types of panels (resizable, draggable, with content dynamically loaded from server, etc.). There is also syntax highlighted code and detailed Howto on integrating the Accordion to a web page. Panels can be re-ordered within the Accordion by drag&drop or undocked (moved out of the Accordion). While undocked they can be further dragged and resized. The whole example is themable; currently there are four themes to choose from.