fakeosx is a GTK 2/3 theme inspired by the popular Mac OS X system that can be used with both Gnome Shell and Unity under Ubuntu 11.10/12.04.
We have previously covered some Mac OS X themes for Ubuntu, you can check them here:
Open the terminal (Ctrl+Alt+T) and install this theme with the following commands:
wget -O fakeosx.zip http://goo.gl/S3NLz
sudo unzip fakeosx.zip -d /usr/share/themes
gsettings set org.gnome.desktop.interface gtk-theme 'osx'
gconftool-2 --set --type string /apps/metacity/general/theme 'osx'
You can also use the MAC OS X icon theme for Ubuntu with fakeosx by running these commands:
sudo tar -xzvf Mac-Lion-Icons.tar.gz -C /usr/share/icons
gsettings set org.gnome.desktop.interface icon-theme 'Mac-Lion-Icons'
To use an app launcher similar to that of Mac OS X, install awn with this command:
sudo apt-get install avant-window-navigator