A multiseat system is a computer set up for multiple simultaneous GUI users, using multiple graphics cards, keyboards, and mice. They're perfect for Internet cafes, library catalogs, kiosk systems, home offices, and even gaming. I've been running a 3- or 4-user multiseat system at my house for almost five years.
PulseAudio, the new GDM, recent X.org releases, ConsoleKit -- Fedora is now a better base for Multiseat than ever before, but it still requires an enormous amount of configuration to get a multiseat system running well.
If you use multiseat systems, or are interested in using them, let's get together during the FUDCon F10 hackathon and plan out a roadmap for making Fedora the best multiseat platform ever.
I have a really old Mini-Howto on this on my blog -- and it still gets thousands of hits a month. I really need to update it with information on other approaches (laptop multiseat and so forth, as well as sound config). You'll see mention of multiseat configuration in the documentation for (the new) GDM, PulseAudio, and so forth.
I'm also interested in multi-seat. I plan on setting up internet cafes in the UK using Linux when I'm older and I'm looking in to different potential configurations. Like Basil, I'd also be interested in extra information on multi-seat. It's the first time I've heard the term.
I myself also made a multiseat for school project ( with use of Gentoo & GDM (Desktop environment KDE)). Chris tyler's article helped me a lot though the Xephyr script still had to be changed way more to let it work with 3 screens! You can check out the site by clicking on my name