The lord king and ruler of the icon creation world is IconFactory. Long a fixture in creating beautiful icons for the Mac, the folks working now are building gorgeous icon sets for Mac OS X.
 
In addition to these lovelies, IconFactory provides software to help you build your own icons. You can also work with them to create custom icons for your own software.
 
The Download button below will open a StuffIt archive with tons of cool icons.
 
NOTE: If you have trouble opening the archive from within your browser, open it from the Images folder in the Finder.