The lineage module adds a table to the taxonomy system that enables sorting
by taxonomy hierarchy for single inheritance vocabularies. It doesn't
provide any obvious functionality to the user by itself, but it does add
another sort option to the views module.

To install:

1) Enable the module in admin/modules.

To Use:

You will probably want the views_bonus_lineage_tree module from
http://drupal.org/project/views_bonus.