Dave,
If you want to group controllers you can do so like this
# /app/controllers/admin/users_controller.rb class Admin::UsersController < ApplicationController end
# /app/controllers/admin/images_controller.rb class Admin::ImagesController < ApplicationController end
Both those controllers are then prefixed by 'admin' (.com/admin/users and .com/admin/images) and look for their views inside of /app/views/ admin.
However for what you're wanting to do I would look into RESTful routes. In app/config/routes.rb you can map resources (controllers) like so:
map.resources :users, :path_prefix => "admin" (available at .com/admin/ users)
the path prefix can be as long as you want, and if you want to get really crazy you do things like this:
map.resources :users do |user| user.resources :images end
then you could have a url like .com/users/9/images/4
peepcode.com have a screencast on RESTful Rails it's well worth spending the $9 on it.
hope that helps!
- Alastair