ruby script/plugin install http://svn.techno-weenie.net/projects/plugins/acts_as_authenticated/

Generate the required code and migrations

ruby script/generate authenticated user account
ruby script/generate authenticated_migration

You can move the

include AuthenticatedSystem

from app/controllers/account_controller.rb to app/controllers/application.rb.
This makes all the authentication methods available to all controllers.

To require logins for all actions, use this in your controllers:

before_filter :login_required

To require logins for specific actions, use this in your controllers:

before_filter :login_required, :only => [ :edit, :update ]

To skip this in a subclassed controller:

skip_before_filter :login_required

Here are other available methods for your views and controllers:

logged_in?

– Returns true if the user is currently logged in.

current_user

– Returns an instance of the currently logged in user.

There is currently no advanced documentation for this plugin.