Here is how to install and use PulseAudio on Xubuntu 8.10 Intrepid Ibex.

1. Install packages for PulseAudio
$ sudo apt-get install libasound2-plugins pulseaudio pulseaudio-esound-compat pulseaudio-module-gconf pulseaudio-module-hal pulseaudio-module-lirc pulseaudio-module-x11 pulseaudio-module-zeroconf pulseaudio-utils paman padevchooser paprefs pavucontrol pavumeter libao-pulse

2. Configure Alsa
Edit the file /etc/asound.conf as root. Create it if it doesn’t exist. Enter the following in this file and save:

pcm.pulse {
    type pulse
}
ctl.pulse {
    type pulse
}
pcm.!default {
    type pulse
}
ctl.!default {
    type pulse
}

3. Add your user account to the pulse groups:

$ sudo gpasswd -a YOURUSERNAME pulse
$ sudo gpasswd -a YOURUSERNAME pulse-access
$ sudo gpasswd -a YOURUSERNAME pulse-rt

4. Configure PulseAudio
Click Applications > Settings > PulseAudio Preferences
On the Network Access tab, check:
- Enable network access to local sound devices
- Allow other machines on the LAN to discover local sound devices
- Don’t require authentication

On the Multicast/RTP tab, check:
- Enable Multicast/RTP receiver
- Enable Multicast/RTP sender

Configure PulseAudio to run as a daemon and allow users to load modules. Edit the file /etc/default/pulseaudio as root.
Change PULSEAUDIO_SYSTEM_START=0 to 1
Change DISALLOW_MODULE_LOADING=1 to 0

Edit the file /etc/libao.conf as root, create it if it doesn’t exist. Enter the following into that file:
default_driver=pulse

Restart your session or reboot to have changes go into effect.

Sources: Ubuntu Wiki, ivotron on Ubuntu Forums, pulseaudio.org