Leopard Quick Look
One of the neatest new features in Apple OS 10.5 (aka Leopard), is Quick Look. The feature enables you to take a peek at most files from within the Finder window, including images, text files, PDF documents, movies, Keynote presentations, email attachments, Microsoft Word and Excel documents. Just select the item and tap the space bar to see a file in Quick Look or press Command-Option-Y to launch Quick Look in full screen mode.