apt-queue would be just as it sounds, a queue for apt. If you are doing a say "sudo apt-get install kubuntu-desktop" but need to install other things after the fact, but don't want to wait around until "apt-get install kubuntu-desktop" is done, apt-queue would allow you to queue apt things. Let's say, while you are installing kubuntu-desktop, you realize you want thunderbird instead of kmail, you would run
sudo apt-queue install mozilla-thunderbird
apt-queue find the pid for the current apt-get process and watches it until it is through, then runs itself. Each apt-queue process would have its own pid obviously, so each apt-queue process would be run in the order the pid was entered on the queue.
