XBMC on Raspbian

Download and install the lastest raspbian to a SD card and boot it on the Raspberry.
Configure it without Window manager, with SSH, 16 MB GPU RAM Overclocking at 950 and the correct timezone and expand the rootfs. Install the rpi-update to update the firmware and so on

apt-get update
apt-get install git-core
wget http://goo.gl/1BOfJ -O /usr/bin/rpi-update && sudo chmod +x /usr/bin/rpi-update
rpi-update
reboot

Enable IPv6 on the PI

# enable it on the fly
modprobe ipv6
#Enable it on the next reboot
echo ipv6 >> /etc/modules

If you overclock then use this tool to watch the temperature:

pi@raspberrypi ~ $ /opt/vc/bin/vcgencmd measure_temp
temp=47.6'C

Now follow this link from step 4.