So here we are, in the modern times with GNOME (I chose that over KDE,
because), and Open Office, Thunderbird, and lots of other nice graphical
apps.

I want to run the apps on an app server and access them for a thin
client.  I am familiar with the K12TLSP project, but right now I want to
see what I can do myself.

What is the minimum X install for the server to run Open Office with the
only graphical usage the remote client?

I don't know about a minimum X install, but I've been very happy with freenx on centos 5, connecting as easily from mac, PC, or linux. in my lab (human brain imaging), we do remote graphics display all the time, openoffice definitely works. I wanted to be able to work from home and X was just crawling along, unusable. with freenx, its almost like sitting at the console. I have my gnome desktop (KDE is also fine) and all the visual goodness that comes with it. my favorite story is an undergrad working in my lab was able to connect over wireless from Argentina to my server in CT USA, pull up images, and do some real work--the point being that its fast and secure.

moreover, there is a very helpful FAQ, http://wiki.centos.org/HowTos/FreeNX

best,

 --Jeremy