I've been having lots of problems with this one...
As some of you have seen, I recently acquired another 22" widescreen panel, which I want to use turned at 90-degrees. I'm also wanting, however, to convert my main system to linux full-time, specifically Ubuntu, for the great third-party driver integration.
I'm using an nVidia card, currently a Geforce 8600 GTS, with the proprietary nvidia drivers. I would prefer to use TwinView, but I can deal with multiple X servers if I need to. I've been researching all over the net the last couple days trying to figure this out, but I can't seem to rotate just one of the displays, leaving the other non-rotated, and it actually work well. The only way that I've gotten even close is using separate X servers and the 'RandRRotation' options in xorg.conf. This gets me the rotation I want, but the lower portion of the screen is unusable and the rotated screen refreshes horribly slowly.