Comment 8 for bug 115745

I think this "bug" should be closed now that nautilus-actions is available in Ubuntu.

To link baobab with Nautilus just install nautilus-actions

sudo apt-get install nautilus-actions

Launch the nautilus-actions configuration tool

System->Preferences->Nautilus Application Actions Configuration

Add a new action

Label appropriately. e.g. Analyze disk usage
Set the tool tip appropriately: e.g. A graphical tool to analyze disk usage.
Set whatever icon you want: e.g. /usr/share/pixmaps/baobab.xpm

Edit the main profile

Set the path to: /usr/bin/baobab
Set the parameters to: %f

On the Conditions tab select to appear only for folders

That's it!