Wikipedia
EGroupware is free open source groupware software intended for businesses from small to enterprises. Its primary functions allow users to manage contacts, appointments, projects and to-do lists. EGroupware is based on PHP. The projects spreads its software under the terms of GNU General Public License (GPL).
It is used either via its native web-interface, making access platform-independent, or by using different supported groupware clients, such as Kontact, Novell Evolution, or Microsoft Outlook. It can also be used by mobile phone or PDA via SyncML.
It currently has translations for more than 25 languages, including right-to-left language support. It depends on a standard X-AMP System and as such requires no specific operating system. Most popular internet browsers are supported for use as web based clients.