EGroupware is a multi-user, web-based groupware suite. Currently available modules include: email, addressbook, calendar, infolog (notes, to-do's, phone calls), content management, wiki, project management, tracker, timesheet, knowledge base, CalDAV/CardDAV
Strange project. A lot of bugs and a very well hidden bug tracker. Seems like the developers try to force the users to buy the commercial support. Additionally this project has a lot of bug regarding the calendar part (iCal/CalDav/GroupDav) which makes it IMHO nearly unusable.