Go to /etc/X11/gdm/custom.conf and manually modify the required fields in the [daemon] section and add the following;
Note: You cannot auto-logon as root.
Bare in mind that I’m not concerned about security at this point as the box is not exposed to the open world, and is somewhat protected by the fact it lives on a “private” LAN. (i.e. my home lan)
If you want to run something automatically on logon you can put the commands into the /etc/profile file. Since I’ve been looking for a way to autostart virtualbox machines this will be the place i do it. (mainly because it is one of the easiest way to do it)