defaults.rb

Merb::Router.prepare do
  
  resources :donors do
    resources :pledges do
      resources :donations
    end
  end

  resources :campaigns do
  
    resources :donors
  
    resources :pledges do
      resources :donations
    end
  end

  resources :pledges do
    resources :donations
  end

  resources :donations
  
end

full.rb

Merb::Router.prepare do
  
  options(:identifier => :id) do
    resources :donors, Donor do
      resources :pledges, Pledge do
        resources :donations, Donation
      end
    end
  
    resources :campaigns, Campaign do
    
      resources :donors, Donor
    
      resources :pledges, Pledge do
        resources :donations, Donation
      end
    end
  
    resources :pledges, Pledge do
      resources :donations, Donation
    end
  
    resources :donations, Donation
  end
  
end