I think you need to install "Gnome Do".
Applications ==> Add / Remove
Search for and install "Gnome Do"
Applications ==> Accessories ==> Gnome Do
and then you can configure it any way you want
You can find more info about it here, courtesy of google http://blog.ibeentoubuntu.com/2009/04/getting-that-os-x-experience-on-ubuntu.html