This script will apply user-entered text to the "Description" tag of each of the selected tracks. iTunes 5.0.1 or better.
(Note: In order to launch this PowerPC-era script on an Intel machine, it must first be opened and then saved using AppleScript Editor, which is located in your /Applications/Utilities/ folder. More information is here.)
Remove iTunes tracks disassociated from files
Restore each selected track's artwork from an image file stored in its Album folder
Append user-entered text to beginning or ending of selected tag of each selected track
App displays files in iTunes Media folder which are not in iTunes library
Set the Album Rating for the album of a selected track to full- and half-stars or computed clear-stars
Create playlists by artist