The fact that Google advertises their servers as supporting CardDAV is an insult to anyone who does try to be standards compliant.

The Google CardDAV server has similarities to what we call CardDAV. For very simple, controlled stuff, it may be possible to pretend it is.

For anything advanced, avoid it at all cost.

SparkleShare is a collaboration and sharing tool that is designed to keep things simple and to stay out of your way.

Syncany is an open-source cloud storage and filesharing application. It allows users to backup and share certain folders of their workstations using any kind of storage, e.g. FTP, Amazon S3 or Google Storage.

SOGo is fully supported and trusted groupware server with a focus on scalability and open standards. SOGo is released under the GNU GPL/LGPL v2 and above.

SOGo provides a rich AJAX-based Web interface and supports multiple native clients through the use of standard protocols such as CalDAV, CardDAV and GroupDAV.

The past four years have been a wild ride for us: growing something from nothing to substantial scale, providing a simple service that people love because it simplifies their lives. We’ve learned tons along the way, often by making big mistakes. We’re really sorry that this last lesson means that you’ll have to find an alternative to Xmarks, but the alternatives exist and you’ll have no problem finding them.

Carry your Google Calendar in your pocket! GCalSync is an open source application that lets you do a two-way synchronization between Google Calendar and your phone's built-in calendar. Download events to your phone, or add an event on your phone and upload it to Google Calendar.

S60Addons.com is a home of few freeware Nokia S60 applications: AutoLock, CalSyncS60 and S60Zip.

The OpenSync project is an ongoing effort to create a synchronization framework that will be a platform independent, general purpose synchronization engine utilizing modular plugins for content formats and different kind of connection types. OpenSync's modularity should allow it to be extended easily to new devices and purposes without radically changing the architecture itself, allowing it to support wide variety of devices used today and in the future.

With libsynthesis, full-featured SyncML functionality based on Synthesis' mature and high quality SyncML DS engine can be integrated into applications. The library provides a stable binary API for both interfacing with the application and for database adaptor plugins.

The Synthesis SyncML engine supports SyncML versions 1.0, 1.1 and 1.2 including complex features like data filtering, suspend & resume, vCard/vCalendar format conversion in a way completely transparent to the user of the library.

Just drag your Folder into Jake and everything will kept in sync with all people you invite.

Jake is 100% free, open source and available for Linux, Windows and Mac OS X. We're using free technologies like Jabber and open source chat server engines.