The LDAP Authentication plugin adds LDAP/ActiveDirectory authentication support for your Retrospectiva installation.
sudo gem install dim-ruby-net-ldap --source=http://gems.github.com
RAILS_ENV=production script/rxm download git://github.com/dim/retrospectiva.ldap_auth.git
RAILS_ENV=production script/rxm install ldap_auth
Visit your Admin / Setup section and adapt the configuration to your Directory setup.