With the unity changes from Natty onward, the traditional Ubuntu gnome taskbar disappeared to be replaced by a set of application panel indicators. I was used to seeing my machine vitals (cpu, network, load etc.) displayed using system monitor in the taskbar. I was pleased to see that this can still be achieved by installing the 'indicator-multiload' package.
Depending on the version you have, the autostart might not work. If it doesn't, just:
and toggle the 'autostart' checkbox under preferences.