If you're lucky Ubuntu will let you know there are Restricted Drivers Available which will get this working better.
Click the little graphics card icon and install the NVIDIA accelerated graphics driver by checking the box under Enabled. That will install the driver and ask you to reboot, so reboot. In my case rebooting disabled my second monitor.Now we need to install the NVIDIA X Server Settings tool. You can search for nvidia-settings in Synaptic to install it, or just open up a terminal and run:
sudo apt-get install nvidia-settings
Then from a terminal run:
sudo nvidia-settings
Click X Server Display Configuration and you should see this:
Click Configure and enable TwinView, then arrange the displays as you'd like them. I ended up with this:
You'll notice I checked Make this the primary display for the X screen in the settings for my larger monitor. This will determin which monitor most things run in, like the login screen and the panel. Click Apply, make sure it looks good, then Save to X Configuration File and finally Quit. At this point it's working but a few things look janky, like your panel runs across both monitors, some screens show up half in one monitor, half in the other, stuff like that. Just loging out and back in clears that up.Enjoy!
Of note, you may later find System -> Administration -> NVIDIA X Server Settings, but that won't really work since it needs permission to write out your new xorg.conf. You can fix this under System -> Preferences -> Main Menu. Click Administration, right click on NVIDIA X Server Settings and select Properties. Add gksu to the start of Command, click Close, and you're set. Next time you run NVIDIA X Server Settings there will be a password prompt and it will be able to write out the configs for you.
