This method doesn't provide 2D acceleration, but works with packages from the official Debian archive. Make sure xserver-xorg-video-fbdev is installed, then add the following line to the default xorg.conf:
Section "Device" Identifier "Configured Video Device" + Driver "fbdev" Option "UseFBDev" "true" EndSection
- Debian Lenny offers GEODE 2.10.0 which includes full XO support and makes the OLPC repository obsolete.
h01ger provides [http://wiki.debian.org/DebianEdu/OLPC/Repositories packages xorg for etch]