The Knight's Calendar has several features, including:

 

Ability to Add/Edit/Delete/View reminders in the calendar
Ability to search all reminders in the system
Ability to add/edit/delete/view reminder types (appointment, birthday, homework, etc.)
Small and compact view to allow for viewing an entire month in one view
Month navigation (forward and back)
Ability to enter date and time of reminders
Plug-in and customize to your site (some code editing involved)
Ability to register multiple users (user registration form) under one account
Easily upgrade to MSSQL with small code changes

Visit http://www.crackheaded.com/knights for demo
Username: guest
Password: guest
-OR- Register to use the calendar for free (non-commercial personal usage)