The Open-Xchange™ Collaboration and Integration Server Environment allows you to create, store and link appointments, contacts, tasks, email, bookmarks, documents, forums and many more elements and share them with other users. This environment can be accessed via any modern web browser and multiple fat clients like KDE Kontact, Apples iCAL, Konqueror, Mozilla Calendar, and many more, based on open standards and interfaces.
If you download the Outlook OXtender, then the Open-Xchange™ Server can also be accessed via MS Outlook and Palm devices. Browse the Wiki and the download section for further information.