The ATI Radeon supports ["AtiHowTo"] open source drivers. However, if for some reason, you prefer to use a closed source proprietary driver, these notes provide installation details.
Official packages
There are official Debian packages containing the proprietary ATI RADEON and FireGL display driver: http://packages.qa.debian.org/f/fglrx-driver.html. Follow the instructions you can find in the README.Debian file(s) shippped with these packages.
Obsolete installer packages
About the obsolete installer packages: As of 2006-04-18, Flavio's [http://www.stanchina.net/~flavio/debian/fglrx-installer.html site] says "These packages are hopelessly out of date and I don't think I'll have time to update them in the near future, because I believe it's more useful to work on the official Debian packages."
External Links
[http://technowizah.com/2006/10/debian-how-to-ati-drivers.html Debian HOW-TO : ATI drivers] explains how to install and configure the latest ATI proprietary drivers using module-assistant and the official ATI installer.
[http://wiki.cchtml.com/index.php/Debian_Installation_Guide Unofficial ATI Linux Drivers Wiki] containing an up-to-date howto to install, configure and test a basic setup with proprietary ATI drivers.
ATI [http://ati.amd.com/support/drivers/linux/linux-radeon.html Automated Installer] released 4/18/2007 - requires installed kernel header package but otherwise no configuration is required
Be aware that upgrading from or to these packages (created by the ATI installer) is and will most probably NEVER be supported by the Debian maintainer of the [http://packages.qa.debian.org/f/fglrx-driver.html fglrx-driver] package(s)!