If an action in one controller leads to a deadly similar template as in another controller, you can just borrow that controller's action template by calling render at the end of your action.

render :template => ''

Say your in tags controller in the show action. You can use the template found in /apps/views/lists/index.rhtml

def show
  [boring action logic]
  render :template => 'lists/index'
end

// description of your code here
In your controller add the name of the .rhtml file in /apps/layouts/ that you want to use, without the suffix (.rhtml).
When rails spits out your view, it will use this given layout as the container for your rendered action.

layout ""