University of Glasgow and Slackware
I just noticed a bit on DistroWatch about a major university's Department of Physical Sciences' migrating their main logon server to Slackware... It seems that the University of Glasgow (in the UK) retired the old logon server because it couldn't handle the load any more. They needed a stable, secure, and easy to maintain operating system for the new one, so they chose Slackware for the job. Thanks to Shane Kelly at UG and anyone else involved in the decision!