Horde Groupware is a free, enterprise ready, browser based collaboration suite. Users can manage and share calendars, contacts, tasks and notes with the standards compliant components from the Horde Project.

This package is part of Horde, a web application Framework written in PHP with modules like IMP (webmail), Turba (contacts), Kronolith (calendar), Nag (task list), Gollem (file manager), etc.