You can download the source code for accordion menu from below link
The attached sample code contains custom menu which can be used in SharePoint as a vertical menu or in any other asp.net web application.
The code sample contains:-
· HTML code for the vertical menu
· CSS for styling on the menu
· JQuery script to provide accordion behavior
· Icons which are rendered as CSS without using any image
For building vertical menu in SharePoint, the attached code can be used in a user control. The attached code renders the menu in aspx page.