http://Yahoo.com has an interesting "feature" operator, e.g.

   foobar feature:table

returns web pages that contain tables, and

   momus feature:audio

contains pages which link to MP3s and other audio files. You can also combine this with the "site" operator, like

   site:blogoscoped.com feature:audio

>> More at http://googlesystem.blogspot.com/2008/03/useful-content-restrictions-for-yahoo.html