jqTree is a jQuery tree plugin with many options and functions. Also it has drag & drop support for tree nodes.
Features
Nestable is an interactive hierarchical list. You can drag & drop to rearrange the order. It even works well on touch-screens.
jsTree is a javascript based, cross browser tree component. It is packaged as a jQuery plugin. jsTree is absolutely free.
jQuery Treeview Plugin is lightweight and flexible transformation of an unordered list into an expandable and collapsable tree, great for unobtrusive navigation enhancements. Supports both location and cookie based persistence.