WebCalendar Hosting
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.

phpicalendar Hosting
phpicalendar is an open source php application to parse and display shared icalendar-compatible calendars on a website. phpicalendar is released under the GNU/GPL terms.

phpScheduleit Hosting
phpScheduleIt is an Open Source web-based reservation and scheduling system, allowing users to register and then place reservations on any kind of resources, such as conference rooms, machines, computers, etc. The administrative side allows complete control over user permissions, resource data, reservation data, and is has many configurable settings.