Ubuntu no longer supplies all of the experimental plugins. Up through Maverick you can use the Compiz Packages PPA and install the compiz-fusion-plugins-unsupported package.
What will work with Natty and Oneiric is the procedure that can be found at UbuntuGuide. Which is to download all of the compiz plugins and rebuild them all from source. This will overwrite the plugins that are already installed via the normal Ubuntu packaging system, as well as adding the unsupported plugins.
sudo apt-get install compiz-fusion-bcop compiz-dev \build-essential libtool \libglu1-mesa-dev libxss-dev \libcairo2-dev git-core
git clone git://anongit.compiz.org/users/soreau/scripts
./compiz-addons install all
nohup compiz --replace &