Building Gentoo for Sheevaplug
First of all, I got an IDE <-> USB converter and plugged a spare PATA 80G disk in my plug. Boot the plug and install Gentoo on the SheevaPlug as you normally would. You can even boot from the USB disk (don't forget to add rootwait to the kernel parameters or it will almost surely complain that /dev/sda1 is not there yet).
When you have the system the way you like it, I made two directories - /mnt/root-src and /root/root-dst then I did the following (you may want to make it a script):
mount -o bind / /mnt/root-src
rsync -avPH /mnt/root-src/ /mnt/root-dst/ --delete --delete-excluded \
q list -o -s gcc portage paludis app-admin/\* app-portage/\* docbooc man