Well, based on the example you provided, there's nothing really magical about how you'd go about it. You'd simply work within Joomla's normal module and templating system.
For the front page, the preview area where they have that news scroller (or whatever you want to call it) ... that would just be a module position. Following that, you have the "alternate footer" with the "event info," "latest news" and "support our team" stuff. That's just another module position.
The module positions for these chunks of content are defined in Joomla's module area. Just make sure you have those positions defined, and select the front page (and front page only) as being the page you want those two module positions to display.
From there, you would just do your normal joomla code in index.php where you check for the active modules. Using the comcast example you provided with the news scroller and the alternate footer ... it would be something like this, hypothetically speaking:
<?php if ($this->countModules( 'news_scroller' ) && $this->countModules( 'alternate_footer_thing' ) ) : ?>
<jdoc:include type="modules" name="newscroller" />
<jdoc:include type="modules" name="alternate_footer_thing" />
<?php else: ?>
// If neither of the modules in question are active for this page, then simply display Joomla's normal content, denoted by the following:
<jdoc:include type="component" />
<?php endif; ?>
That's roughly how you would go about it. Very roughly.