Quick Look is absolutely one of the best features in Leopard, and is a huge productivity booster. Click on any file and hit the spacebar, and boom (think John Madden), you see the contents of the file. This works great, except when you are missing a Quick Look Generator to expose the contents of the item. Leopard doesn't ship with very nice plugins for Folders, ZIP files, or DMGs. By nice, I mean it only shows a much larger version of the items' icon and some pretty big text with standard file or folder properties. I want to see inside everything using Quick Look. Fortunately, Apple has a Quick Look Programming Guide and a developer/designer pair have implemented their own ZIP and Folder generators:
I installed both earlier today and so far they work great and provide exactly the functionality you want from a Quick Look Generator.