OS X 10.8 and later only. This script checks your entire iTunes library for missing and presumed dead tracks--those tracks that iTunes is unable to associate with a file and which are listed in iTunes with a "!"--and can create a text file listing these tracks by alleged File Path (if available), Song Name, Artist and Album, which you can view using TextEdit.
Also see Music Folder Files Not Added
To find and delete dead tracks see Super Remove Dead Tracks.
See the video on YouTube.
iTunes can't find the files pointed to by the Location property of these track entries.
Resample selected tracks' artwork to user-set size limit
Gather audio tracks whose files contain no artwork metadata
Copy selected tracks or playlist to a new iPod, iPad, or iPhone playlist
Put file creation date to each track's comment tag
Export album artwork as folder.jpg to Album folder
Edit a selection of iTunes tracks' tags in single window