It's easy as 1, 2, 3.
1. Open ShareMusic
2. Add a personal message (optional)
3. Press the Share button
It also lets you control your music playback right within the app and change the message format.
It will share these information on your wall:
- Song title
- Artwork and link to the iTunes Store
You need to be logged in a Facebook account. Artwork and link to the iTunes Store might not represent the current playing song if the album/artist information is not
- Fixes for OS X 10.8 Mountain Lion
- Adds an option to keep the window visible after sharing is done