Running Google searches for specific file types

It's well known that you can search for specific file types in Google by structuring a search in this form:

filetype: pdf

This search will only return pages to which PDF images have been post.ed A search for:

filetype:mbox -site:facebook.com

. . . will exlcude hits for .mbox files on the Facebook site. A search for: "filetype:mbox site:facebook.com", will only find.mbox files on the Facebook site.

A search for:

ext: ppt

. . . will also only find files with the extension for PowerPoint, ppt. .ext is a simple variation on the filetype search.