For those unfamiliar with Drupal it is a largescale opensource CMS for a website which is used by the likes of Tim Berners-Lee.
Drupal is scalable and modular built which even includes design elements. Each Drupal website is like a house built out of legos -- just like legos fit together to create something (a working door, a roof, etc.) which then creates the overall house, the modules fit together to create larger functionality, which in turn, creates the website.
Sounds confusing? Not really these days. The initial versions of Drupal were not so user friendly -- figuring out which module went with which version and which module was needed for which functionality was sometimes hard (and complicated!). Early themes were very bland and all had a very Drupalesque view. At that time, it was very easy to figure out if a site was running Drupal. If the look didn't give it away, then the urls (node!) would!
The latest version continues to move forward -- even the actual Drupal website is getting more user friendly. Although the ability to search for modules by version at the website has existed for a while, it now clearly states which module (or theme) works with each version. Upgrades are getting easier to do, too. With the creation of the Zen theme (CSS based) and with some of the newer themes also supporting CSS, getting a more personalized look is becoming easier, too. The Pathauto module (version 5+) allows the user to create personalized and relevant URLs, e.g., mysite/resume vs. mysite/node/1
Finally, Drupal continues to shine at what it has been good at: providing web editors with a means to design a website by moving the construction and design away from the content creation. By having the content creation separate, adding content to a Drupal website can be a simple as posting to a blog. Of course, user authority levels and passwords are part of that, too.
Drupal does lack in some specialized functionalities such as creating an e-publication and e-portfolios. Given that Drupal is highly customizable and many of the modules can (and do) work together, there are many different ways to create more specialized functionalities such as e-publication and e-portfolios.
Drupal also has limited support for crosswalking third party applications. However, it does seem like support for third party applications is becoming more common, and with widgets being developed (or already available) for many of the common web 2.0 sites (flickr, youtube, etc.) it is easy enough to incorporate those bits of code into Drupal.
Drupal has recently branched off into a commercial project which is working with Millenium (III). I hope that there is no negative impact on the opensource project, as there has been with Joomla (a rival opensource CMS, for which most of the advanced functionalities are fee based).
Libraries or library related organization using Drupal: NW Central , Standford Univ. Information Center, Fish4Info (library portal), and there is even a module to import MARC into Drupal!
Drupal screenshots including behind the scenes are here.
Oh, and my little e-portfolio.