How to find manually installed packages?

With this suggestion, I'm assuming your old installation will still boot!

To replicate one set of packages on another machine:

On System A, run:

dpkg --get-selections | grep -v deinstall > my-selections

Move the my-selections file over to System B.

On System B, run:

dpkg --set-selections < my-selections

and then:

sudo apt-get dselect-upgrade

Important note: if you have installed packages from non-standard repositories and/or PPAs, you will also want to copy /etc/apt/sources.list and the contents of /etc/apt/sources.list.d/ from System A to System B before you run the upgrade.

You can use dpkg to see what you've removed as well (NB: this will also include packages that you manually installed and removed):

dpkg --get-selections | grep deinstall

You can see your results in the terminal, or, of course, redirect to a file.

This thread from superuser.com gives this solution:

aptitude search '?installed ?not(?automatic)'

If your apt logs are in /var/log/apt, something like this should work:

gunzip -c /var/log/apt/history.log.*.gz | grep "apt-get install"

Or if you want to get rid of some of the repetitive junk in the output:

gunzip -c /var/log/apt/history.log.*.gz | grep "apt-get install" \
  | cut -f4- -d" " | sort | uniq