WebCalendar

WebCalendar is a PHP-based calendar application that can be configured as a single-user calendar, a multi-user calendar for groups of users, or as an event calendar viewable by visitors.

Homepage: http://www.k5n.us/webcalendar.php/
Disk Space: 3.5 MB
Documentation: http://www.k5n.us/webcalendar.php?topic=Documentation
License: GPL