Baïkal - Cal and CardDAV server
SOGo - SOGo is groupware server with a focus on scalability and open standards.
Radicale - The Radicale Project is a complete CalDAV (calendar) and CardDAV (contact) server solution.
Xandikos - Lightweight CalDAV/CardDAV server on top of Git.
Roundcube - Web-based IMAP email client
CalendarServer - CalendarServer is a standards-compliant server implementation of the CalDAV and CardDAV protocols, including iMIP and APNS.