All of our hosting plans have WebCalendar pre-installed

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. MySQL, PostgreSQL, Oracle, DB2, Interbase, MS SQL Server, or ODBC is required.

WebCalendar can be setup in a variety of ways, such as...

A schedule management system for a single person
A schedule management system for a group of people, allowing one or more assistants to manage the calendar of another user
An events schedule that anyone can view, allowing visitors to submit new events
A calendar server that can be viewed with iCalendar-compliant calendar applications like Mozilla Sunbird, Apple iCal or GNOME Evolution or RSS-enabled applications like Firefox, Thunderbird, RSSOwl, FeedDemon, or BlogExpress.

Overview of Features

XHTML/CSS compliance
Multi-user support
30 supported languages: Basque, Bulgarian, Chinese-Big5, Chinese-GB2312, Czech, Danish, Dutch, English-US, Estonian, Finnish, French, Galician, German, Greek, Holo-Big5, Hungarian, Icelandic, Italian, Japanese, Korean, Norwegian, Polish, Portuguese_BR, Portuguese, Romanian, Russian, Spanish, Swedish, Turkish, Welsh
Auto-detect user's language preference from browser settings
View calendars by day, week, month or year
View another user's calendar
View one or more users' calendar via layers on top of your own calendar
Add/Edit/Delete users
Add/Edit/Delete events
Repeating events including support for overriding or deleting (exceptions)
Configurable custom event fields
User-configurable preferences for colors, 12/24 time format, Sun/Mon week start
Online help
Checks for scheduling conflicts
Email reminders for upcoming events
Email notifications for new/updated/deleted events
Export events to iCalendar, vCalendar or Palm
Import from iCalendar, vCalendar or Palm
Optional general access (no login required) to allow calendar to be viewed by people without a login (useful for event calendars)
Users can make their calendar available publicly to anyone with an iCalendar-compliant calendar program (such as Apple's iCal, Mozilla Calendar or Sunbird)
Publishing of free/busy schedules (part of the iCalendar standard)
RSS support that puts a user's calendar into RSS (WebCalendar 1.1+)
Subscribe to "remote" calendars (hosted elsewhere on the net) in either iCalendar or hCalendar formats (WebCalendar 1.1+)
User authentication: Web-based, HTTP, LDAP or NIS