Links

Debian GNU/LINUX
A free, UNIX-like operating system.
Ubuntu
Free and user-friendly operating system based on Debian. Ubuntu was the basis for LEARNIX from 2008 to 2010. It still is the mother of Xubuntu.
Xubuntu
GNU/LINUX distribution based on Ubuntu. The main difference is that Xubuntu utilises the XFCE destop, rather than GNOME3 which is rather clunky.
Radiance
Physically-correct ray tracing software.