Commercial/iOS
2Do is a task (to-do) manager for iOS that uses CalDAV to store and access the task remotely.
Open Source/Android
aCal is a CalDAV client for Android which requires a CalDAV server to function.

Open Source/multilanguage
AgenDAV is an open source multilanguage CalDAV web client which features a rich AJAX interface with shared calendars support.
Android
AnDal is a Calendar app for Android that synchronizes with calendar servers supporting the CalDAV protocol.

Included with Mac OS X
Desktop client for Mac OS X that supports CalDAV Access and Scheduling.
Included with iOS 3 and up
Client for iPhone/iPod Touch/iPad that supports CalDAV Access. iOS 4 adds implicit scheduling support.
Included with Atmail Product PHP/Zend, jQuery
* A complete Ajax Web Calendar which supports creation of events, tasks, and allow users to schedule work and appointments
* Daily and weekly calendar view included
* Intuitive Web interface for creating, moving and resizing scheduled events
* View shared Calendars, users availability and all the features you'd expect in a groupware solution
* Support for IE, Firefox, Safari, Chrome and modern browsers
* Delegation support for shared Calendars

Commercial product only, server- or cloud-based solution, requires minimum 10-user license
Commercial/Mac OS X
BusyCal is a desktop calendar that allows families and small workgroups to easily sync calendars with various CalDAV servers.
Commercial/iOS
BusyToDo is a simple To Do list manager for iOS that syncs tasks via CalDAV.
Commercial/Outlook plug-in
The WebDAV Collaborator is a powerful plug-in for synchronizing your CalDAV calendar and/or CardDAV contact data to Outlook.
Open Source Android Sync Adapter
CalDAV Sync (Free)" by Gérald 'gege' Garcia is an Android sync adapter that enables you to use the (usually pre-installed) default Android calendar app together with a CalDAV server of your choice.
Android
CalDAV-Sync is a CalDAV client for Android to sync events. It is strictly a sync adapter and requires an existing calendar app or component.

Open Source Web Client
CalDavZAP is an open source CalDAV web client
Android
CalendarSync syncs your device with various calendar information sources, e.g. it allows you to sync Android with CalDAV. It also provides many additional features.
Open Source/Cross-platform
Desktop client that includes CalDAV Access support.

Not supported since 2009
Open Source/Android Sync Adapter
DAVdroid is a professional open-sourc synchronization adapter that combines CalDAV and CardDAV into one Android+ app. It offers two-way sync, integrates seamlessly into the device and is aimed at easy setup and simplicity.
Creative Commons/Drupal
dCaldav is a lightweight, read-only caldav Drupal calendaring client. It comes as a Drupal 6 module with a block included.
GPL/Joomla
DPCalendar is a full responsive Joomla calendar which integrates any CalDAV server seamless into Joomla. You can modify the events right into DPCalendar and the changes will be written back to the CalDAV system (two-way sync).
Free/Windows
Desktop client for Windows (.NET) that supports CalDAV Access.
Commercial/iOS
eTask is a task (to-do) manager for the iPhone that uses CalDAV to store and access the task remotely.
Commercial/Windows
EVO Collaborator for Outlook (ECO) enables users to take advantage of CardDAV for Contacts and CalDAV for Calendars and Tasks. Synchronization of both Contacts, Calendars and Tasks occurs whenever changes are made. By supporting iCloud, Gmail, fruux, Yahoo! (read-only) and AOL (read-only), users easily import what they have on cloud. Yet, C2C (Cloud to Cloud) feature facilitates duplicating your contacts and calendars from one place to another; O2C (Outlook to Cloud) feature gives you an option saving your data elsewhere on the Cloud.
Open source/Linux
Evolution provides integrated mail, addressbook and calendaring functionality to users of the GNOME desktop.
Outlook for Windows Sync Plugin
iCal4OL is a program for smart importing with sync, exporting and subscribing (as Remote Calendars) ICAL files (*.ics) and feeds in Outlook 2000-2010.
Open Source/Joomla
jCaldav is a lightweight, read-only caldav Joomla calendaring client. It comes as a Joomla 1.5 extension as both a component and as a module.
Open Source/Java
The Calendar Portlet is a JSR 168 read-only calendar aggregator portlet. This portlet allows a user to view built-in default calendars and add external iCal feeds for display, and includes support for CalDAV servers.
JavaScript CalDAV Client
A CalDAV Client for modern( ca. 2011) web browsers using a bit of html5 and a bunch of css3. Patches, bug reports and translations of the en-us.js file are welcome, send to rob+jqcaldav@boxacle.net.
Open Source/Linux
Plugin that provides CalDAV support for Kontact.
Android
Kalendi Android is a calendar application for Android that supports multiple CalDAV servers.

Free API package available.
Open Source/Python
khal is a CLI (console/terminal) calendar application build around CalDAV. Seeking more users to test the application.
Open Source/Cross-platform
Desktop client (Sunbird) and Thunderbird plugin (Lightning) that supports CalDAV Access and Scheduling.
Open Source/Cross-platform
Desktop client that supports CalDAV Access and Scheduling.
Open Source/Windows
Outlook plugin that supports CalDAV Access and Scheduling.

Not supported since 2008, appears to be abandoned. Does not work with current versions of Outlook.
Commercial/Mac OS X & Windows
Postbox is a Mozilla-based email application that now supports the Mozilla Lightning extension to enable access to calendars directly within the application, including CalDAV servers.
Multi-Platform calendar client
Rainlendar runs on Wndows, OS X and Linux and is available in both a free Lite and purchased Pro version with more functionality including CalDAV support.
Commercial/iOS
RemoteCalendar is able to directly access CalDAV calendar data on iOS.
Commercial/Windows
SimpleCal is a Windows calendar application built on top of the CalDAV standard.  It currently supports Windows Vista, Windows 7, and Windows 8.1.  Visit www.ligaturetech.com for more information.
Commercial/Mac OS X
Application to manage both personal and shared calendars.
Open Source/Linux & Windows
Spicebird is a collaboration application built on top of various other open source software, mainly the Mozilla Platform and Thunderbird. CalDAV support is included.

Status uncertain; appears to have been abandoned since 2009
Commercial Outlook/CalDAV Sync
SurGATE Outlook Sync Client provides two-way calendar and contacts sync between Outlook and CalDAV/CardDAV Servers.
Open Source/Java
TaskCal Internet standards based human task management and process interaction. TaskCal is an iCalendar wrapper to the jBPM process manager, providing standards based calendar agent access to an actors tasks via email (iMIP), HTTP (.ics) and CalDAV.
Open Source/Java
Webical is a web application to view and edit multiple iCalendars and has a CalDAV plugin. Its features include progressive enhancement, a plugin framework that can be used to enhance the GUI and the back end providers, pluggable authentication, and i18n.