Wowhead is a database of World of Warcraft information. The database provides a hierarchical subject taxonomy to describe items, and presents that hierarchy in the breadcrumbs for the item. When the user hovers ofer a branch in the breadcrumb trail, a drop down menu is displayed to show the node siblings and drill down to children.

1. Single entry view (database record).
2. Hovering over the current entry's parent category (Daggers) to view siblings.
3. Hovering over the grandparent category (Weapons) to view its siblings (other grandparent categories).

http://www.wowhead.com/