Here's a neat trick that is fairly pointless, but fun nonetheless. When minimizing a window, or bringing it back out of the dock, hold down the shift key, and watch as it shrinks/expands in slow motion. This also works with some other aspect of the UI, such as Exposé, opening multiple mail threads, using the login window and changing view in address book.

If you want to see any application do something in slow motion, hold down the shift key and see if it works!