One of the last major projects I was privileged to work on (along with some other awesome colleagues) while I was working as the Director of Web Development for the Archdiocese of St. Louis (see 'A New Job' on my blog for more info) was the Eucharistic Congress website and video.
One of the major benefits of using a robust content management system like Drupal (which archstl.org uses) is that you can actually build 'special sites' that highlight certain events or causes without building an entirely separate website. For example: Every organization in the Archdiocese has it's own website, with its own content managers, its own forms, news pages, articles, etc. through the use of Drupal's 'Organic Groups' module.
For the 2011 Eucharist Congress, instead of building a separate website, and then linking back to the Archdiocesan website, we built a single page template for the Congress home page (using a standard Drupal template (.tpl.php) file), and then set up all the rest of the content (a registration form, some information pages, etc.) in Drupal.
The results are pretty impressive (you have to visit the site to see the jQuery-enabled page load effects, which look great on any device—no Flash here!):
In addition to this awesome website (the front end was designed by Ben G., who works in the Archdiocese's Catholic Youth Apostolate), an excellent video highlighting the Eucharist was produced, and is visible (in HD!) on YouTube:
Kudos to the team who helped with all of these promotional materials for the Eucharistic Congress! I think this raises the bar, or at least pushes it a little, for Catholic dioceses hoping to spread the word about their larger events!