As gusty is comming soon, I need to keep a list of my currently installed packages in order to reinstall (most) of them if I make a fresh install (actually update-manager allow to upgrade the distribution when a new one comes, but there is sometimes weird behaviors with this method). So here’s my little command to perform that:
the geek way :

dpkg -l | grep '^ii' | awk '{print $2 $3}' > mypackageslist.txt

the debian way (but packages names are incomplete) :

dpkg --get-selections

voila