Models: acts_as_nested_set acts_as_list acts_as_tree http://www.oreillynet.com/ruby/blog/2006/07/treemap_on_rails.html
Controllers: http://pezra.barelyenough.org/blog/2007/07/hierarchical-resources-in-rails/
Do any of those help? You could also simply setup your models appropriately and use some type of parent_id as a foreign key.
Regards, Michael Guterl