Please note that I have made these changes in accordance with the ubuntu forums suggestions on twinview, and only after successfully installing the nvidia proprietary drivers which are availble on their website
http://www.ubuntuforums.org/showthread.php?p=1773584
http://www.nvidia.com/object/linux_d..._1.0-9755.html
I have used this method in Slackware 11, Ubuntu Edgy & Drapper, Debian Etch, but not Debian Sarge (I'm sure it would have worked if I hadn't given up so that I could upgrade to Etch, which by the way seems much easier to work with)
this is, obviously, only the device section of my /etc/X11/xorg.conf
Section "Device"
Identifier "NVIDIA Corporation NV43 [GeForce 6600 GT]"
Driver "nvidia"
Option "TwinView" "True"
Option "TwinViewOrientation" "RightOf"
Option "UseEdidFreqs" "True"
Option "MetaModes" "1280x1024,1280x1024; 1024x768,1024x768"
Option "UseDisplayDevice" "CRT"
EndSection
I hope this helps. I love having two monitors, for what I do it helps.