<p>I have a rails application running on a Linux server. I would like to interact with Outlook/Exchange 2003 appointments from the rails application. For example, certain actions should trigger sending an appointment, and then preferably accepting/canceling the appointment in Outlook should trigger events in the application.</p>

<p>Failing this, is it possible to publish calendars that Outlook 2003 can read without requiring Outlook plugins? I note that Outlook 2003 does not support ical without plugins for example. Similarly, if this is not easily doable in Ruby, but is in another language (such as Perl for example) running on Linux then those suggestions would be welcome.</p>

<p>Any advice on how to achieve this, or where to start looking for answers would be gratefully received.</p>

Outlook appointments are just e-mails with special header information. There's some information in
this tutorial
on the required parts.  I sent a few meeting invites from my Outlook to my Gmail account and took a look at the raw headers there - you can figure most of the protocol out from that.
The
iCalendar specs
may help you, as well.