Leopard’s Quick Look allows you to view the contents of a file (html, text, etc) without even opening it. You can also watch a full-screen video with just a single click (spacebar). However, if you do a Quick Look on a folder, it will not show you the folder’s contents. So a developer, Taiyo, created a plug-in for Quick Look that allows you to view the folder. There is also a plug-in to view zip files.
Awesome work Taiyo.