Calendars are a great way to let users know what's coming up with your site in the near or distant future.

A Calendar of Events in CGI - By Collin Forbes
This CGI script will create an output of a calendar for just about any month by entering in the month and year. Automatically enters major hollidays such as Thanksgiving etc, but doesn't let user enter his or her individual ideas automatically. Useful if you just want a quick calendar print out. Click for demo.

Groupware Calendar - By Selena Sol
Calendar allows for multiple entries to one date. Clicking on a date brings up a type of "day at a glance" feature which divides the day up by hours. With the click of a button users can post events or change the day, month, and year. Click for demo.

HyperCal - By Richard Bowen
Creates an nice looking calendar but has other features that other scripts don't. Marks the current date in red on the calendar and designates a picture for each of the months to make scheduling far in advance easier. When appointments are added, each day gets its own web output to make reading it easier. Click for demo.

PerlCal - By Randal Pittelli

Good script that makes a beautiful done calendar. Appointments for each day can be devided into different sections so this calendar is good for people that have many different appointments each day. Uses many images to enhance the look of the output as well. Also uses frames. Click for demo.

WebEvent - By Cameron Consulting
One thing I notice right away that I personally don't like is that the titles of the events are added right to the main calendar. This can be good for some people but if you have a lot of items for a particular day it may be a bit difficult to read the calendar. Each appointment does have its own page output though and when creating appointments, it does give the option of either plain text or HTML. Click for demo.