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, Song Name, Artist and Album, which you can view using TextEdit.
OS X 10.6 and better only. Universal version for PowerPC machines available at the link below in the "Info" section.
Also see Music Folder Files Not Added.