Quick How-To: Login without a password, Debian/Ubuntu using GDM

Why? (Yes, I know you wanted to ask)
He's three - he can pick his picture from a list, but asking him to remember his password is pushing it a bit I think...

This isn't as easy as you'd think. For the whole dirty story, see this Launchpad entry.

For the quick how to

Make it possible to log in on a console without a password by starting up a terminal and typing:
sudo passwd -d usernameGoesHere

Change the login screen to use a list of users you can click on by going to System -> Administration -> Login Window and after putting in your password select the Local tab. Under Style, pick one of the options that mention a face browser.

Still won't work yet though :-) Last, add 128 (yes, 128) lines to /etc/securetty
It should look like this

# Local X displays
:0
:0.0
:1
:1.0
:2
:2.0
:3
:3.0
and keep going until you hit 63

Hope this helps...