I keep getting inquiries about multiseat X configuration under X11R6.9. Here is a temporary mini-Howto document that I've put together. I'll write a better one when X11R6.9/7.0 is finalized (and time permits ) ... and there will be a chapter on the topic in one of my upcoming books.
In the meantime, have fun! -- please let me know what experiences you have trying this out (positive or negative) -- in particular, it would be great to have reports on which video card combinations work or do not work.
(For those new the term "Multiseat X", it means creating a system with mulitple video monitors, keyboards, and mice for simultaneous use by multiple users -- like my home system).