Note: ID3Mod is no longer under development, although the download is still available.
ID3Mod can change the encoding of MP3 ID3 TAG information. It's very useful when you copy PC encoded MP3 files to Mac, while the song name maybe in a mess when you import them into iTunes.
ID3Mod can access iTunes song library, so you can modify the songs tag encoding even you already import them into iTunes.
One unique thing about ID3Mod is that it handles encoding with DBCS (Double Byte Character System) like Chinese, Japanese, Korean or any other non-ISO-8859-1 encoding. This means the tags will be comatible when imported into iTunes.