I launched this site today, it's pretty cool.
Basically it suggests songs to you that you wouldn't normally have or listen to, but are still good. It's kind of like a reversed iTunes Genius… it actually more of a iTunes Librarian that can help you find interesting books to read by just showing up to the library with a list of what you already have… except, for music. hah.
So yeah, basically the site works for just about anyone with any usable information in their iTunes Library (whether it be star-ratings or only Play Counts, as well as other factors like quantity of songs by that particular artist, etc.) — so give it a try and grab some new tunes from those artists you already know and love! http://ilikebsides.com