So what did I installed on my IBM x60s?
cat /var/lib/portage/worldshows you all the packages you have ran 'emerge package'. It will not show you all the dependencies that portage have added, so its a clean list of packages you installed.
I copy the world file to my fresh install and edit it deleting packages I don't need.
But wait! Don't install this packages yet. You will download lot of blobs that you have already.
In my x60s all the packages are stored in /usr/portage/distfiles/.
So I just copy all the files from the old computer to the new computer. I do it with rsync, but you can do it with scp, cp+sshfs etc.
rsync -avPn --exclude=svn-src /usr/portage/distfiles/* x200/usr/portage/distfiles/Lets make sure we have all the blobs:
emerge --fetchonly $(cat copied.world.file)
Now we can install everything ;-)
emerge $(cat copied.world.file)