Paul Newman

A simple but effective Calendar plugin for WordPress that allows you to manage your events and appointments and display them to the world on your website. The Plus is that Two seperate calendars may be used. Also a smaller displayed version of the Calendar to better fit into page or post content. 
This can be used as a drop-in replacement for the original Calendar plguin.
Features:
<ul>
<li>Monthly view of events</li>
<li>Mouse-over details for each event</li>
<li>Events can have a timestamp (optional)</li>
<li>Events can display their author (optional)</li>
<li>Events can span more than one day</li>
<li>Multiple events per day possible</li>
<li>Events can repeat on a weekly, monthly (set numerical day), monthly (set textual day) or yearly basis</li>
<li>Repeats can occur indefinitely or a limited number of times</li>
<li>Easy to use events manager in admin dashboard</li>
<li>Sidebar function/Widget to show todays events</li>
<li>Sidebar function/Widget to show upcoming events</li>
<li>Lists of todays events can be displayed in posts or pages</li>
<li>Lists of upcoming events can be displayed in posts or pages</li>
<li>Comprehensive options panel for admin</li>
<li>Modifiable CSS using the options panel</li>
<li>Optional drop down boxes to quickly change month and year</li>
<li>User groups other than admin can be permitted to manage events</li>
<li>Events can be placed into categories</li>
<li>A calendar of events for just one of more categories can be displayed</li>
<li>Categories system can be switched on or off</li>
<li>Pop up javascript calendars help the choosing of dates</li>
<li>Events can be links pointing to a location of your choice</li>
<li>Full internationalisation is possible</li>
<li>Comaptible with WordPress MU</li>
<li>Two seperate Calendars can be setup and used</li>
<li>Calendar can be full-size or small size to fit into page or post content</li>
<li>Drop in replacement for original Calendar plugin</li>
</ul>

Calendar Plus

A simple Calendar plugin for WordPress that allows 2 seperate calendars. This can be used as a drop-in replacement for the original Calendar plugin.

fullthrottledevelopment

Michael Torbert

A calendar plugin supporting multiple calendars, recurring events, and several different widgets / shortcodes. More info at http://calendar-plugin.com
Basic features include:
<ul>
<li>Recurring Events</li>
<li>Multiple Color Labels</li>
<li>Multiple Shortcodes and Widgets</li>
<li>Full sized calendar</li>
<li>Sexy Google Calendar UI</li>
<li>Events can be attached to any Post, Page, or custom post type</li>
<li>Premium support and custom development available</li>
<li><a href="http://calendar-plugin.com/quick-start-guide" rel="nofollow ugc">Quick Start Guide</a></li>
</ul>
Premium features available:
<ul>
<li>Display schedule information within post content</li>
<li>iCal feeds</li>
<li>SMART event ordering for WordPress queries</li>
<li>RSS 1.0 & 2.0, ATOM, and RDF feeds</li>
<li>Backup & Export FullThrottle Calendar data to a CSV file</li>
<li>Import FullThrottle Calendar data from a CSV file</li>
<li>Import Event Calendar 3 data from the WordPress database</li>
</ul>
<h3>License</h3>
FT Calendar 
Copyright (C) 2011 Full Throttle Development, LLC.
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see <a href="http://www.gnu.org/licenses/" rel="nofollow ugc">http://www.gnu.org/licenses/</a>.

FT Calendar

A calendar plugin supporting multiple calendars, recurring events, and several different widgets / shortcodes. More info at http://calendar-plugin.com

Calendar Plus vs FT Calendar