If you are using Django, http://bitbucket.org/tabo/django-treebeard/overview http://bitbucket.org/tabo/django-treebeard/overview, is a great app to use. It impl

If you are using Django, http://bitbucket.org/tabo/django-treebeard/overview http://bitbucket.org/tabo/django-treebeard/overview, is a great app to use. It implements several different tree storage methods.