The Ranting Beaver

Here's a way to have Google help you find a certain file:

-inurl:(htm|html|php) intitle:"index of" +"last modified" +"parent directory" +description +size +([file_extension]) "[search_term]"

Simply use the string above, replacing the following:

[file_extension] with any file extension -- jpg, pdf, mpg, m4v ... and so on
[search_term] with a word you want to search for, such as naruto

For example, pasting the following in the search box in Google:
-inurl:(htm|html|php) intitle:"index of" +"last modified" +"parent directory" +description +size +(mpg|mpeg) "anime"

Will return you pages where there are mpg or mpeg files with the word anime in the filename. Try it!