Radicale - A simple CalDAV (calendar) and CardDAV (contact) server

Radicale is a free and open-source CalDAV and CardDAV server. It shares calendars and contact lists through CalDAV, CardDAV and HTTP, Supports events, todos, journal entries and business cards. It works out-of-the-box, no complicated setup or configuration required. It stores all data on the file system in a simple folder structure.