Unofficial drivers for ATI Radeon (789)xxx on CRT display works courtesy of Philippe Anel's. There are reports that it works on TFT displays on some IBM T30 thinkpads.
The homepage for the drivers is http://web.archive.org/web/20041030113126/http://mapage.noos.fr/philippe.anel/plan9rxxx.html
For using the Radeon in Plan 9, you need to compile the Radeon driver of Philippe Anel into the kernel. For my Radeon, I used:
with the driver posted on 22 March 2004:
and the vgadb extension from:
NOTE: The original host for the drivers is down, the links now point to the archive.org mirror, I also mirrored them in /n/sources/contrib/uriel/mirror/philippe.anel/radeon/
An updated (July 2009) version of the driver that builds against recent Plan 9 kernels is available at http://endeavour.zapto.org/src/radeon.