I don't know if I'm seriously behind the curve on this, or if I've found something new, but:
I know the conventional wisdom: If you run two monitors on one graphics card, you can only calibrate one monitor. In fact, I've seen the same information on the Datacolor/Colorvision website. But wait, there's more......
I just added a second monitor to my digital darkroom, to improve my Photoshop workflow. Of course, I had to replace the graphics card to make this work. I chose a Diamond Stealth X1050 card (who dreams up these names?) with Radeon driver software. The card has two output connectors, one VGA and one DVI (requires a DVI to VGA adapter). After installation, I was surprised to find that my Windows Device Manager showed two separate drivers running, one for each monitor. I decided to try a test, and ran my usual Spyder2 Pro calibration on each monitor. There is now a different ICC profile loaded on the card for each monitor, and changes to one does not affect the other. Life is good!
This is not only a surprise but a relief. My expansion ports are maxed out and I have no room for a second graphics card.
So, is this really working, or am I delusional?