In the past I have already addressed The argument publishing guides on how to make a desktop based on KDE but VERY VERY similar to Mac OS X.
Course required to carry out different operations and take care of the issues individually.
Today I propose instead a complete package: Phoenix Mac4Lin ver.1.0 Released! .
Unfortunately it is only available for the GNOME desktop environment such as Ubuntu, for example, and does not run on KDE desktop, as Kubuntu.
The appearance more interesting is that this package not only deals with changing the desktop and windows to catch the apple style, but also various external programs such as Firefox, Thunderbird and Rhythmbox.
The result is quite good: