Sharing a calendar between two or more people should be fairly cheap, and reasonably simple to accomplish; however, most of the time it isn't. Google provides an excellent calendar service that meets my needs, but some people absolutely require the ability to do their calendaring in Outlook. Previously, that meant a lot of headaches — either from using Exchange or trying to figure out a way not to use it. Fortunately, Outlook 2007 provides the ability to publish calendar files in .ics format to a WebDAV server, and subscribe to similarly published calendars.
Additionally, Apache2 makes it easy to get WebDAV working, by providing mod_dav and mod_dav_fs (I recommend using auth_digest as well for enhanced security over basic authentication). In Apache 2.x on Debian, enabling modules is as simple as running a2enmod. After enabling the required modules, insert the following into /etc/apache2/httpd.conf:
Next, you'll need to configure the auth_digest permissions for the directory by running htdigest -c /etc/apache2/passwd.dav webdav . It will ask you to setup a password for the username you specified — this will be how you access the calendar file. Reload the Apache2 configuration by running /etc/init.d/apache2 force-reload so it will recognize your changes.
In Outlook 2007, go to Calendar and right click on the calendar name. Then go to Publish to Internet -> Publish to WebDAV server. You'll want to use the directory you just setup on your web server — something like http://www.domain.com/calendar/, if you used the /var/www/calendar/ path from my example. You'll need to use the username and password you setup with auth_digest access earlier. One nice feature is that Outlook allows you to publish calendars with varying levels of detail, ranging from full details to only showing availability. Also, you can limit published calendars to only show working hours, and even define what those hours are.
So for easy calendar sharing, it would be easy enough for each person to publish their calendar to a server and have the other members of the group subscribe to it. That wasn't too painful was it?