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.
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.
(via in-app purchase)
Perhaps Also of Interest...
downloaded 4m 37s ago
Applet compels you to rate unrated current track
downloaded 5m 55s ago
Displays files in iTunes Media folder not in iTunes track library
downloaded 8m 43s ago
Gather audio tracks whose files contain no artwork metadata
downloaded 11m 11s ago
Perform search-and-replace on text in your choice of tags
downloaded 12m 21s ago
Two scripts copy text from clipboard to current or single selected track's lyrics tag
downloaded 14m 16s ago
Rename selected tracks' Song Names with their filenames (minus extension)