- Baïkal, a lightweight CalDAV+CardDAV server
- Balsa a lightweight email client for GNOME
- Calendar Lock PEA, encrypted calendar application
- Chandler - As of 2012, there have been no releases for over two years and the project seems to be orphaned.
- Citadel
- CiviCRM - customer relationship management software
- Claws Mail (the vCalendar plugin is required to handle iCalendar in Claws Mail)
- Darwin Calendar Server
- DAViCal server for calendar sharing
- Dolibarr ERP & CRM
- Drupal with its event module
- etm (text based event and task manager) export to iCal
- Evolution the Gnome email/calendar client
- Hippo CMS
- Horde
- Joomla there are several plugins available
- Kontact (namely KOrganizer and KMail)
- Lightning (Mozilla extension for Thunderbird mail/news client and SeaMonkey internet application suite)
- Mozilla Thunderbird mail/news client (with Lightning extension)
- Moodle will export iCalendar data or let you subscribe to a Moodle iCalendar feed.
- Mulberry
- Org-mode - an Emacs mode for organising your life.
- OLAT - LMS supporting import and export of personal and shared calendars via iCalendar
- Open Atrium - Drupal based
- Opengroupware.org
- Open-Xchange
- Orage - part of the Xfce desktop, can import and export .ics files.
- Osmo (PIM)[1]
- ownCloud - cloud storage and services including WebDAV, CalDAV and CardDAV.
- phlyMail (groupware)
- PHP iCalendar - viewer/parser to display iCals in a Web browser
- Plone open source content management system
- Request Tracker - a ticket-tracking and call-center application. Exports iCalendar data.
- SeaMonkey internet application suite (with Lightning extension)
- Semantic Mediawiki semantic extension to MediaWiki
- Simple Groupware
- SOGo - a integrated groupware with Apple iCal, Mozilla Thunderbird support and native Outlook compatibility
- SPIP a CMS that allows the export of its site calendar in the iCalendar format.
- Tiki Wiki CMS Groupware Calendar exports to iCal and generates hcal
- Tryton
- Sunbird (a Mozilla stand-alone application, discontinued)
- TYPO3 via its Calendar Base Extension
- vTigerCRM (CRM)[2]
- WebGUI - an open source content management system written in Perl
- Webical
- Web2project
- Wordpress via plugins
- YaMA - Yet another Meeting Assistant
- Zarafa Collaboration Platform
- Zimbra Collaboration Suite
- Zotonic via mod_calendar
==Attribution==
- based on http://en.wikipedia.org/wiki/List_of_applications_with_iCalendar_support and used with permission under CC-BY-SA