Charles Retina Institute, Tennessee, USA
We use Debian/i386 on one server that lets us do backups of Windows workstations using smbfs, mail service with exim, antivirus checking using amavis, file service using samba, web development using Perl and Template Toolkit, and a plethora of administrative tasks.
We found Debian simpler to maintain than the alternatives, and the support, on the mailing lists, can't be beat.