I use this in a nightly cron job to have an updated list of my system's packages:
dpkg --get-selections > packages.txt
Then on my local system I use this to sync the packages up manually:
sudo dpkg --set-selections < packages.txt
sudo apt-get dselect-upgrade
This is an old article but it does contain some helpful responses from the readers:
http://www.ubuntugeek.com/clone-your-ub ... ation.html
One last thought, you might want to consider chroot, I'm not a pro (only used it once) at using it but it might let you image your server, copy it locally then access it in a chroot without the booting mess ... maybe (not totally sure).