So last week I posted on lkml an old patch that we were carrying for a long time in the Linux community. It basically brings the multiple (old) video cards functionally again on Linux and X server (and this time doing on the right and beauty way). For the people that was following multiseat implementations, this is a HUGE step: we will finally be able to discard the old and ugly hack (a mix of Xorg, several Xephyr servers + evdev) and and go to a clean way, starting multiple X servers in parallel. Cool! Well, not that much, because it might take some time to be in your beloved distribution :)
It’s too early and I don’t know if it’s recommended to say this, but if you want to give a try basically you have to get all X components, this X server patches, my libpciaccess and Dave’s kernel patchset. Again: it’s a very unstable work!
If you’re concerned with the technical explanations then you can follow the nice memo that Dave wrote about this.