DAVx⁵
ownCloud is a PHP-based file sync and share solution. It can be extended with apps for Contacts, Calendars and Tasks.
CalDAV/CardDAV setup
To use both CalDAV and CardDAV in the same account and just using the host name as URL, configure well-known URLs (recommended).
OwnCloud 9:
Base URL: /remote.php/dav/ (e.g. https://server.example/owncloud/remote.php/dav/)
OwnCloud 8 and below:
For CalDAV use: /remote.php/caldav/ (e.g. https://server.example/owncloud/remote.php/caldav/)
For CardDAV use: /remote.php/carddav/
Contact group method: groups are per-contact categories
User name and password: same as in ownCloud
(LDAP authentication may cause problems with certain OwnCloud apps)
Troubleshooting
Most problems can be fixed by upgrading to the newest OwnCloud version (don't forget to update the Contacts, Calendar and Task app, too).
WebDAV setup
You can mount folders of your ownCloud using the DAVx⁵ WebDAV mounts feature.
WebDAV URL: https://{domain}/remote.php/webdav.php or https://{domain}/files/webdav.php
User name: your owncloud email address or username
Password: your password