OS X 10.8 or later. This application will list the file paths of the files in your designated "iTunes Media" folder which are not in iTunes' track library. Additionally, you can select a different parent folder and its contents will be compared to the iTunes library. Includes options to Add a selection of found files to iTunes, move them to the Trash, and export a text file listing the file paths.
See the video on YouTube.
These files are in my "iTunes Media" folder but do not exist as track entries in iTunes. The tracks may have been deleted from iTunes but, for whatever reason, I did not choose to move their files to the Trash.
Load this script in your Login Items to activate an iTunes playlist at startup
Use tag data to formulate new file name for selected tracks' files
Display, create text file listing info of dead tracks
Resample selected tracks' artwork to user-set size limit
Batch-reset the Start and Stop Time of selected tracks to their entire duration
Set the Plays of selected tracks.