gistfile1.rb

ActionController::Routing::Routes.capture(:my_plugin_or_whatever) do |map|
    map.resource :plugin_stuff
    map.connect "/plugin/:blah", :controller => "whatever"
end

gistfile2.rb

ActionController::Routing::Routes.draw do |map|
  map.resource :app_things

  map.include :my_plugin_or_whatever

  # etc...
end