Departamento de Arquitectura y Tecnologia de Sistemas Informaticos, Universidad Politecnica de Madrid, Spain

We use Debian GNU/Linux on our servers and workstations. They are running NFS, NIS, CVS, Apache, FTP, DNS, POP, IMAP, SMTP on over 15 servers. We are very happy because it's too easy to configure and administrate, and it's Free Software.