AppleInsider in part of their Road to Mac OS X Leopard articles has posted on an evolution of Mac OS X finder from System 3.0 until yet to release Mac OS X Leopard finder. Finder is an integral part of Mac OS X and it is a simple file utility that ran as default application when the systems started. Its like windows explorer for Windows OS but with more functionality and nice looking.
In Leopard, Apple will introduce Coverflow and Quicklook as a default feature for finder. Even though its not quite useful unless you view picture in finder, but I am sure it will continue Apple tradition in making something looks good.
You can read the full article here and you can see how the finder has evolved.