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.)
Emulates iTunes search and copies results to a playlist
Update subscriptions which have expired by virtue of being ignored for five or more days
Delete characters from the beginning or ending of selected tracks' name, artist, album, comments, composer, or show tags
Change file type to make selected AACs bookmarkable
Applet assists with swapping, copying, appending data between track tags
Perform search-and-replace on text in your choice of tags