GNU/Linux
Qoting Wikipedia1: Linux is a free and open-source, monolithic, modular (i.e., it supports the insertion and removal at runtime of loadable kernel objects), Unix-like operating system kernel available for a variety of hardware architectures (like i386 or AMD64). We are using Linux on a wide range of systems, from service servers, compute cluster, staff and student workstations. The ISG.EE systems are set up using the Debian GNU/Linux Distributions.
Configurations - Hints for configuring Linux
Applications - Using some selected Linux applications
Software - List of available software on Linux (you can also use the comandline tool sepp)
Distributions - Used distributions and other distributions.