jqTree is a jQuery tree plugin with many options and functions. Also it has drag & drop support for tree nodes.
Nestable is an interactive hierarchical list. You can drag & drop to rearrange the order. It even works well on touch-screens.
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.