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.
Gather all tracks of selected tracks' albums to single playlist
Edit a selection of iTunes tracks' tags in single window
Remove iTunes tracks disassociated from files
Exports and then re-imports selected tracks' artwork
Export selected tracks' data to XML file, import later
Resample selected tracks' artwork to user-set size limit