CardDAV services
Apple/iCloud
Sign-up required
iCloud Contacts is CalDAV Enabled.
EGroupware
Free Trial/Hosted in Germany
Hosted EGroupware enterprise groupware server including CalDAV and CardDAV support.
FastMail
Free Trial/Premium
Keep on top of your events, meetings and day-to-day tasks with calendars and contacts that work across all your devices.
fruux
Synchronization Service
fruux is compatible with CalDAV and CardDAV.
GMX.net
Free/Premium Service GERMAN only
The new GMX.net address book also offers CardDAV.
GMX.com
Free
The new com address book also offers CardDAV.
Landmarks
CalDAV/CardDAV service
Landmarks is a CalDAV/CardDAV service available initially in Germany.
Memotoo
Synchronization Service
Memotoo is compatible with CalDAV and CardDAV.
Servermx.com
E-Mail/CalDAV/CardDAV service
servermx.com offers e-mail hosting plus Contacts and Calendars via CalDAV and CardDAV support.
Yahoo! Contacts
Yahoo Contacts allows syncing Apple’s Address Book with the Yahoo! CardDAV server (and presumably others).
WEB.DE
Free/Premium Service GERMAN only
The new WEB.DE Contacts also offers CalDAV.