I have configured the Cinnamon desktop environment to look like Mac OS X.
First, you have to get the Cinnamon desktop and Cairo Dock. Cairo Dock is already in the Ubuntu Software Centre, so you can get it from there.
To get cinnamon, open a terminal and type in these commands:
Then log out and log back into Cinnamon. Open Cinnamon Settings, go to Panel Settings and there will be a option ot make the panel go to the top. There is also a Windows setting manager, where you can move your window controls to the left in the desired order that they should appear. Get the Mac OS X Theme for Ubuntu from Noobslab.com and install it. Activate Cairo Dock and get any themes you want from the Cinnamon Spices website and you will have a Mac OS X lookalike(with a start menu).
sudo add-apt-repository ppa:gwendal-lebihan-dev/cinnamon-stable
sudo apt-get update
sudo apt-get install cinnamon
I use 12.10.