Add filters for PDF, Word, and Excel files in the media library

showmimes.php

<?php
/*
Plugin Name: Show MIMEs
Description: A tiny plugin to add more file type filters in the media library screens.
Author: Stephanie Leary
Version: 1.1
Author URI: http://sillybean.net/
*/


function tvmdl_show_mime_types( $post_mime_types ) {  
	$new_mime_types = array(	//	array( adj, noun )
		'application/pdf' 	   => array( __( 'PDFs' ), __( 'Manage PDFs' ), _n_noop( 'PDF <span class="count">(%s)</span>', 'PDFs <span class="count">(%s)</span>' ) ),
		'application/msword' 	   => array( __( 'Word Docs' ), __( 'Manage Word Docs' ), _n_noop( 'Word Doc <span class="count">(%s)</span>', 'Word Docs <span class="count">(%s)</span>' ) ),
		'application/vnd.ms-excel' => array( __( 'Spreadsheets' ), __( 'Manage Spreadsheets' ), _n_noop( 'Spreadsheet <span class="count">(%s)</span>', 'Spreadsheets <span class="count">(%s)</span>' ) ),
	);
	
	return array_merge( $post_mime_types, $new_mime_types );  
}  

add_filter( 'post_mime_types', 'tvmdl_show_mime_types' );