Search Google by file extension

Ever want to search the web for an Excel spreadsheet checkbook? Easy. Type filetype:xls checkbook into the search box at Google.

Behemoth search engine Google indexes more than just web pages. Narrow your search down to specific types of files with the "filetype" directive.

How about PDF's on productivity? Or PowerPoint presentations (filetype:ppt) on web development? Or Beethoven MP3's? Or Britney Flash (filetype:swf) movies? Or BitTorrent files (filetype:torrent) named something like, um, Sopranos? Just sayin'.