Of course, my laptop only has one VGA out port, so I can only physically connect one extra monitor (the laptop's LCD serves as the primary display). So, I had an idea: connect one monitor to my (currently) headless Linux box, and use VNC to connect to my laptop and display the right-most third of my extra-wide desktop.
It turns out that there doesn't seem to be a good way to do that. Windows thinks there's only two monitors, so the desktop won't extend past what's visible by the first two monitors. I found a program that uses a custom driver to do the same thing I want to do, but unfortunately VNC isn't able to see anything on the virtual monitor. I was thinking of setting my video card's drivers to use a virtual desktop that's bigger than the physically displayed one, but it seems that nVidia pulled that feature out of their drivers. I suppose I could always downgrade my drivers?
Anyway, it seems like the ideal situation would be to have a driver that emulates the video card, which would have two main advantages: my desktop would actually extend to a third virtual monitor, and the driver knows EXACTLY what's been updated on the display, so VNC doesn't have to keep polling. Ultr@VNC seems to use this approach, but the driver is binary-only for some reason (while the rest is open source), and that kinda scares me.