It’s been six weeks since Leopard was released on October 26th. One of the most talked about feature was Quick Look, in Quick Look you can look inside any document without launching an application. You can use Quick Look in Finder, Mail and Time Machine. Quick Look makes it easy to view full-screen preview of the files, flip through multi-page documents and add image directly to iPhoto. You can quickly preview multiple files at once in a table view or individually with slideshow controls. By just pressing the space bar in Finder you can view the content of the selected file/files. Though Quick Look is a very helpful feature it has its limitations, if a folder is selected you just see the size of the folder but you don't get any information about the files inside the folder, its same for the zip files too. There is a work around for this problem you can download folder and/or zip plugin that would show details about the files in the folder or zip file. The plugin increases the functionality of an already excellent feature. To install the folder and/or zip plugin just drag the plugin (Folder.qlgenerator or Zip.qlgenerator) into /Library/QuickLook and relaunch Finder.  You can get more details about the plugin on the website.
Quick Look Folder Plugin
Quick Look Zip Plugin