NOTE: I'm using files and disk images I had already acquired/created for sheepshaver under windows. You will need a ROM image and a disk image with Os9 already installed for these instructions to work.

get necassary files/libraries
sudo apt-get update
sudo apt-get install libgtk1.2
sudo apt-get install alien

download sheepshaver rpm to desktop

cd ~/Desktop
sudo alien -k SheepShaver-2.3-0.20060514.1.i586.rpm
converts rpm with alien to deb

sudo dpkg -i sheepshaver_2.3-0.20060514.1_i386.deb
to install or double click the deb file (and no that's not a typo, the rpm labeled "i586" creates a deb file on my desktop "i386", go figure)

cd /usr/share/SheepShaver
SheepShaver
gui to configure, find your hd image, rom, and other settings...I had coppied my ROM and HD files to the /usr/share/SheepShaver directory

NOW I've also got Sheepshaver running on my Intel Macbook under Os X! http://www.scothiam.com/content/sheepshaver-os-x-intel

...if I can only get them networked...

Links:
http://ubuntuforums.org/showpost.php?p=1498088&postcount=6
http://gwenole.beauchesne.info/en/projects/sheepshaver/help/installation
http://ubuntu.wordpress.com/2005/09/23/installing-using-an-rpm-file/