I finally got 1680x1050 resolution working on my GeForce 8600 GT and Acer 22" widescreen LCD.  I used the Wubi installer for this which made it super easy to dual boot with Vista, however on the login screen I kept getting an "Out of Range" error using the built in OSS nVidia (nv) drivers.  After some reading I found that I would need the nVidia provided binary drivers to get dual monitors working anway, so I thought I would see if this would allow me to run at the native resolution of my monitor.  Of course I found that my particular video card, GeForce 8600 GT, was not supported by the nVidia binary driver installer.  I ended up doing a manual install of the drivers which actually worked, unlike the untold number of xorg.conf edits I made previously.

1. Download the NVidia binary drivers from their website.
2. Change to command line (CTRL ALT F2), and shutdown your display manager: sudo /etc/init.d/gdm stop
   
3. Install the dev libc libraries since no precompiled libs exist for my Ubuntu version.  sudo apt-get install libc-dev.
4. Install the drivers: sudo sh NVIDIA* -k (run this from the location you downloaded the binary drivers too).
5. Follow the install instructions, when prompted allow the installer to configure your xorg.conf file.