There are two ways to create a list of installed packages:
1. quoted from here,
To output this information to a file in your home directory you would use,
dpkg --get-selections > installed-software
And if you wanted to use the list to reinstall this software on a fresh ubuntu setup,
dpkg --set-selections < installed-software
followed by
dselect
2. quoted from here,
"dpkg -l" provides you with the full list of installed packages, if you only want to know the names and put them in a txt file
dpkg -l | awk '{print $2}' > installed_packages.txt
if you install a new box, just install the base system without any packages (don't use tasksel and / or deslect) and run
apt-get install `cat installed_packages.txt`
