Ive created a package to install and configure XGL/Compiz with Gnome as part of a larger project called AfterBirth.

There are two ways to install: method 1 uses the full AfterBirth app, method 2 just installs the afterbirth-xgl-gnome package.

Method 1

Code:
sudo apt-get update && sudo apt-get upgrade
sudo cp /etc/apt/sources.list /etc/apt/sources.list.afterbirth-`date +%Y%m%d%H%M%S`
# Make sure universe is enabled
echo 'deb http://archive.ubuntu.com/ubuntu/ dapper universe' | sudo tee -a /etc/apt/sources.list
echo 'deb http://www.voxpopulimedia.com/debian dapper main' | sudo tee -a /etc/apt/sources.list
sudo apt-get update && sudo apt-get install afterbirth
After installation, run `afterbirth` from the command line or Applications > System Tools > AfterBirth. Select 'Gnome Eyecandy' to install XGL/Compiz.

Log out. Select Xgl from Sessions menu and log back in.

Please report your AfterBirth experience to this thread.

Method 2

Code:
sudo apt-get update && sudo apt-get upgrade
echo 'deb http://www.voxpopulimedia.com/debian dapper main' | sudo tee -a /etc/apt/sources.list
echo 'deb http://www.beerorkid.com/compiz/ dapper main ' | sudo tee -a /etc/apt/sources.list
sudo apt-get update && sudo apt-get install afterbirth-xgl-gnome
Log out. Select Xgl from Sessions menu and log back in. Your fancy new eyecandy should start up immediately.