As I was traversing the Internet, I found a great post about Operating System Interface Design Between 1981-2009 showing a range of GUIâ€™s that have been developed for different operating systems such as OS/2, Macintosh (Mac), Windows, Linux, Symbian OS, over the years.
To me, the most amazing evolution is the one for the famous Macintosh. Mac has been known for great user interfaces and great products like iPhone, iPods, etc. and therefore great to see how their GUIs have evolved.
Check out the details at Webdesigner Depot.