Describe AtiHowTo here.
For the moment: Flavio Stanchina provides an installer-package for the proprietary ATI graphics drivers. You find the package and a how-to at http://www.stanchina.net/~flavio/debian/fglrx-installer.html or http://xoomer.virgilio.it/flavio.stanchina/debian/fglrx-installer.html.
As of 2006-04-18, Flavio's site says "These packages are hopelessly out of date and I don't think I'll have time to update them in the near future, because I believe it's more useful to work on the official Debian packages." The Debian-QA page for the latter is here: http://packages.qa.debian.org/f/fglrx-driver.html