_delete.html.erb

<%= highlight(t(:'.confirm', :resource => resource, :default => :'delete.confirm'), resource.to_s) %>

<%= semantic_form_for resource, :html => { :method => :delete } do |form| %>
  <%= form.buttons do %>
    <%= form.commit_button :delete %>
  <% end %>
<% end %>

add_delete_to_resource_routes.rb

module AddDeleteToResourceRoutes
  class Railtie < Rails::Railtie
    initializer "add_delete_to_resource_routes.initialize" do |app|
      ActionDispatch::Routing::Mapper::Resources.class_eval do
        def resources_with_delete_action(*resources, &block)
          resources_without_delete_action *resources do
            yield if block_given?

            member_scope do
              get :delete
            end
          end
        end
        alias_method_chain :resources, :delete_action
      end
    end
  end
end

gistfile3.txt

See my blog post about this at http://amielmartin.tumblr.com/post/1216720481/delete-action-in-rails-3