Adds a global addressbook to Roundcube with contacts from CiviCRM. Requires database access to the civicrm database.
cd your-roundcube-folder/
cd plugins
git clone https://github.com/jaapjansma/RoundcubeCivicrmAddressbook.git civicrm_addressbook
Edit config/config.inc.php:
$config['plugins'] = array(..., 'civicrm_addressbook');
$config['civicrm_db_dsn'] = 'mysql://civicrm_db_user:civicrm_db_password@localhost/civicrm_db';