Retrieve list of installed packages, Save a list of all programs installed on Ubuntu

Next week I will make an installation of Ubuntu 11.04 beta 2 (64 bits) from scratch, but I will not lose the programs that I have currently installed. I searched on the solution to this problem is that with a single command can save a list of all packages installed on our current Ubuntu installation. The procedure is as follows:

First keep the list:dpkg --get-selections | grep -