I had a look through the system library in the Finder's Cover Flow mode and discovered that quite a lot of icons still are in the old 128px size ... but what surprised me was the fact that Quartz Composer files automatically started to play. To have a look at these, just navigate to the main screen saver folder (/System » Library » Screen Savers). There you will have Arabesque, RSS Visualizer, Shell, Spectrum and Word of the Day playing directly in Cover Flow mode. Very nice if you ask me!
[robg adds: You can also, as you might expect, use Quick Look on a Quartz Composer file and watch the animation in a larger window.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20071126165348345