Dries is the founder and project lead of Drupal and co-founder of Acquia and Mollom.
We're on a roll with universities using Drupal! Portland State University (PSU), with more than 24,000 students, is using Drupal for their main website at http://pdx.edu.
See this list for dozens more K-12 schools and universities using Drupal: http://groups.drupal.org/node/11258
Of course there are actually thousands more, just not all are on that list.
We switched our department over to a drupal site with support for student accounts, blogs, and groups with wikis and news. It's been great since all us faculty (and students) can update content ourselves instead of going through one webmaster. I've also used it in support for many of my classes.
Here's a description:http://edtechdev.blogspot.com/2008/07/department-20.html
and I even published an article about it:http://jolt.merlot.org/vol5no2/holton_0609.htm
In the class I'm teaching now for example we created a wiki-based educational technology 'knowledge base':http://itls.usu.edu/groups/foundations2009
The University of Northern Iowa will be coming soon... new designs are being developed, hopefully we'll have a new main university site up in Drupal by the new year. We already have around 15 sites in production in Drupal, with dozens more in development.
Just wanted to correct one thing in regards to the Portland State University Drupal comment. You stated that they are using it for their main site, which is true, but they are also running close to 100 sites using the Drupal multi-site features as well as a syndication system to share data between all their sites. You can see more details at http://www.swipht.com/portland-state-university-mutli-site-drupal-instal... .
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