Quick Tag for Mac

From Mac Appetite:

• Tag songs in iTunes for easy organization and better smart playlists!
• Launch Quick Tag with a user definable global hot key
• Quickly tag the song that is currently playing, or tag whatever songs are selected in iTunes
• Existing tags are auto-suggested when entering a song's tags
• Existing tags can be read from iTunes for auto-suggestions
• Rich support for tagging multiple songs at once. Add tags to the selected songs, remove tags from the selected songs, or replace the tags of the selected songs
• Rate the song at the same time you tag it, with the built in rating control
• Tags are saved to either the 'grouping' or 'comment' field in iTunes
• Configure how your tags are stored internally in iTunes
• Support for existing internal tag formats
• Optionally, starts playing a specified playlist in iTunes upon activation
• Multi-word tags are supported
• Displays information about the song you are currently tagging
• Lightweight and easy to use