This script will apply user-entered text to the "Category" tag of each of the selected tracks. iTunes 5 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.)
Export artwork of selected tracks to parent or specified folder
Sort purchased tracks into discrete playlists by name or account ID
Exports and then re-imports selected tracks' artwork
Paste text contents of the clipboard to each of the selected tracks' Lyrics tag
Apply selected CD's CD Text to its disc and track tags
Enter text for the selected tracks' Long Description tag