Remove annoying update pop-ups from Ubuntu Oneiric(12.04)

Open /etc/xdg/autostart/update-notifier.desktop, find NoDisplay and edit it to false.

...
Icon=update-notifier
Exec=update-notifier
Terminal=false
Type=Application
Categories=
NotShowIn=KDE;
NoDisplay=false
X-GNOME-Autostart-Delay=60
X-Ubuntu-Gettext-Domain=update-notifier

Update-notifier will then show up in the application gnome-session-properties, where it can be disabled. When disabled, a modified version of update-notifier.desktop is written to ~/.config/autostart/.