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.)
Edit a selection of iTunes tracks' tags in single window
Rename selected tracks' Song Names with their filenames (minus extension)
Use tag data to formulate new file name for selected tracks' files
Exports and then re-imports selected tracks' artwork
Remove iTunes tracks disassociated from files
Append user-entered text to beginning or ending of selected tag of each selected track