Ok, i got it:

The search option "isTagged:false" is my friend now! Nice... ;-)

Yup, you got it. Someone on a GTD blog post somewhere saved this search as a Smart List with the list name "!". I've followed suit and it's a nice to have and very compact Smart List. Happy RTM-ing.

Do you or someone else remember where to find this GTD blog post?

Here you go -- it's a screencast.
http://ryan.mcgeary.org/screencasts/RTM-GTD-Conventions/

Thanks alot... :-)