I was going to recommend AptonCD. I use it to keep my downloads on a
DVD and works great. You can install from the CD or DVD the
applications you want to re-install. The process is manual not
automatic meaning you will have to select the desired apps at time of
install.

Any packages that are not open you should download to a file and make
a copy on CD for later use.

I have used tar to backup my system according to the forums on the
Ubuntu site, but I have to fix the grub after updating the system from
the image I have saved, I am sure there is a fix for this, the problem
I get is the UUID are a perfect match and my expermental system
conflicts with grub data.