This document intend to describe how I managed to get a PC with :
Such configurations are often called multiseat linux, multi-seat linux, multiuser X11, or some variations around those themes.
Also, most of this setup can be used in order to produce more than two full featured independent X-servers : users regularly reported 3 and sometime up to 5 or 6 seats, though in my opinion, it might lead to a bunch of wires.