I'm migrating my PostNuke site over to Drupal. While I've been able to figure out how to set the theming, blogging, and module systems to my satisfaction, one area I'm still having trouble with is integrating custom/external content. The best way to describe what I'm trying to do would be to show an example. Please check out the "Open Source" and "DailyStrips" sections of my current website at http://www.legroom.net/. Both of these show unique examples of what I'm trying to do.
The Open Source section consists of a bunch of different html pages that are included depending on which subsection is selected. All of this is controlled by an index.php file that includes a few lines at the top for PostNuke initialization, such as pulling in the header, setting the theme, checking authorization, etc.
The DailyStrips section is very similar, again a collection of separate pages linked together. The reason I also mention this one is that it ties into PostNuke's authorization system, so I can restrict it to authenticated users. Also, while the Open Source section is largely static and could be converted over to Drupal "pages", DailyStrips relies on externally generated content, so it has to be able to read directly from the filesystem.
Neither of these are true PostNuke modules; I simply added a few lines to the top of the main index file to basically wrap PostNuke around the content.