OS X 10.8 or later. Append the same user-entered text to the beginning or ending of the existing text in the chosen tag (Song Name, Artist, Album Artist, Album, Composer, Comments, Genre, Grouping or Show Name, and their Sort siblings) in each selected track.
For tags other than "Song Name" and "Show Name", this script may be just slightly less involved than performing a multi-edit on the selected tracks.
Also see This Tag, That Tag.
Preview each track as it will appear after applying the entered text.
Export album artwork as folder.jpg to Album folder
Exports and then re-imports selected tracks' artwork
Restore each selected track's artwork from an image file stored in its Album folder
Enter text for the selected tracks' Description tag
Edit a selection of iTunes tracks' tags "old-school"
Remove iTunes tracks disassociated from files