Great post jalind!
I was able to get my onboard Mobility Radeon x600 working with your tutorial.
One thing I had to deviate from was step 4, since the x600 has 64MB of integrated video memory, I skipped this step as I don't need POSIX support.
One other note, to get up and running, I had to edit the xorg.conf file (sda3/changes/etc/X11/xorg.conf - YMMV) for the card to be recognized. I added the following to the end of the file:
After a reboot, all was working great. Thanks again for the great tutorial!