Simple Groupware is an open source enterprise application offering email, 
calendaring, contacts, tasks, document management, synchronization with 
Outlook and cell phones, full-text search and many more.

Simple Groupware combines standards like RSS, iCalendar, vCard, IMAP, POP3,
SMTP, CIFS, CSV, WebDAV, LDAP and SyncML under one platform. Unlike other
groupware software, Simple Groupware contains the programming language sgsML
to enable the quick customization and creation of powerful web applications.

WWW: http://www.simple-groupware.de/