Well I finally got the ATI firegl driver working for my Radeon 9000 under Debian Sid running Linux kernel 2.6.4. Since this was a bit of a hassel for me I thought I'd write it down so I don't have to figure it out again later and so anyone else who needs it can hopefully find the information out there somewhere!
This is all pretty Debian specific, I'm sure it's just as easy under redhat or whatever, but we all know that Debian is better ;-)
If I've got anything wrong here or if there is a better way to do this, please let me know by emailing:
dmcgraw AT watchland.org
download the RPM from ATi (for XFree 4.3)
Install the kernel headers for your kernel
apt-get install kernel-headers-`uname -r`
Install the kernel-source package for your kernel
apt-get install kernel-source-<ver>
Create a symlink for /usr/src/linux to the kernel-headers. Technically this isn't needed, but it makes it easier to keep things straight.
ln -s /usr/src/kernel-headers-`uname -r` /usr/src/linux
Perform some version specific magic
Build & Install the module
Optionally (but I recommend it to at least learn the options you can use) run fglrxconfig to generate a XF86Config-4 file
Edit a couple of locations in the ATI make.sh script. Really you just need to check/set 2 variables.
First search for linuxincludes. Make sure that is set to /usr/src/linux/include (if you made the symlink above).
Then search for drmincludes. Make sure that is set to /usr/src/kernel-source-<ver>drivers/char/drm
Create a symlink for the modules build directory
ln -s /usr/src/linux /lib/modules/`uname-r`/build
Change the kernel headers to reference the kernel source package's drm include
tar -jxvf kernel-source-<ver>.tar.bz2
mv drm drm.original
ln -s /usr/src/kernel-source-<ver>drivers/char/drm drm