I Love Stars
"Easily rate your songs from the menubar"
This is great because it also has the ability to remind you to rate an unrated song when it's nearing its end. Rating with this is easier than using Bowtie or other iTunes controllers, since you don't have to switch apps (given the case you don't use hotkeys).

GimmeSomeTune
"With GimmeSomeTune, you can download lyrics and album covers..."
This happens automatically in the background for songs that don't have lyrics or artwork yet. Has many more features.

Boffin
"Boffin is Last.fm radio, for your local music..."
Scans your iTunes library and enables you to play your local music sorted by genre(s) with the help of Last.fm metadata.