I just got a second monitor at home and wanted to configure the two monitors with my NVidia graphics card. You can set up TwinView in the Nvida Settings application, however I did not like that solution: the next time I restarted X, all the settings were lost and the second monitor powered off. Also GNOME did not seem to behave correctly when the monitors went on stand by and I unlocked the desktop. The desktop appeared to be shifted over the monitors. The latter might be a bug of gnome-settings-daemon 3.2 and not Nvidia’s however.
However since the NVidia proprietary driver version 330 beta series, it finally supports Randr 1.3 so that you can configure dual screen with the configuration tools provided with your desktop. This driver is currently available in Debian Experimental. To install it (make sure you have experimental in your apt sources.list first, of course), run this command:
# apt-get install -t experimental xserver-xorg-video-nvidia
I also pulled in gnome-settings-daemon and gnome-control-center version 3.4 which appeared in Debian Sid today:
# apt-get install -t unstable gnome-settings-daemon gnome-contol-center
Now reboot your system (to be sure the new Nvidia kernel and X drivers are loaded), and then go System Tools – Preferences – System Settings (gnome-control-center in a terminal window) – Display. Enable the wo monitors, set the optimal (highest) resolution and drag them in the right position, click Apply, and confirm everything is working fine. Now you have a nice multi-monitor setup without needing to mess with NVidia’s twin view and without having to create a script to get the right settings applied automatically when X is started.