From Silly Bit:
Libra is a very simple application that allows you to create, use and manage multiple iTunes music libraries. Normally, iTunes has only one library, but with Libra you can have any number of distinct libraries, each located wherever you want.
- Allows to create new libraries.
- Allows to rename and delete libraries.
- Automatically quits and relaunch iTunes when switching library.
- Localized in many languages.