dhtmlxTree represents hierarchically organized data in the best way and allows you to create user-friendly navigation system.

This JavaScript Tree Menu can load its content dynamicaly from server using Ajax or directly from on-page XML data-island. The tree has cross-browser compatibility, powerful JavaScript API, drag-n-drop functionality, built-in checkboxes and context menu. There are CF and JSP tags and ASP.NET custom control for the tree.

The tree control is free for non-commercial use.