iWork files are really just zip files, and contain PDF previews
Have you ever received an iWork file created in Pages, Numbers, or Keynote on a Mac, and not had any way to deal with it? Next time, try changing the file's extension to .zip, then unzip it with your favorite zip utility. Inside you should find a PDF preview document containing a nicely formatted version of the document in question.
It seems strange that Apple doesn't promote this fact more, as it's a real usability win for iWork users that want to share their documents with non-Mac users. Wouldn't it be nice if Word, Excel, and Powerpoint did this?
[photo by *keng]