ActiveRbac is a Ruby On Rails plugin that supports you in implementing Role Based Access Control (RBAC) in your application.
At the moment, active-rbac is being rewritten. The new version - to be named 0.5.0 - is currently only available from SVN trunk.
$> cd $RAILS_ROOT $> svn co svn://rubyforge.org/var/svn/active-rbac/active-rbac/trunk/plugin \ vendor/plugins/active-rbac
There also is a branch called rails-1.2 of the old 0.4.0 active-rbac version available that runs with Rails 1.2 and is based on Rails Engines.
$> cd $RAILS_ROOT $> svn co svn://rubyforge.org/var/svn/active-rbac/active_rbac/branches/rails-1.2/active_rbac \ vendor/plugins/active_rbac