I don't know if this is new in eMusic or if I only just noticed it, but it's kind of cool. It generates recommendations of artists you might like based on what you've already bought, which is nothing new. But the visual display of it is pretty slick. You can see which recommendations come from which other users via which artists, and you can watch the connections change just while you mouse over the different names in all three columns. Plus, of course, you can play samples right there. Nice.
The problem here is that I don't really have a reason to care much about things eMusic is recommending based on just a couple months of purchases. What I want is this UI on my Last.fm recommendations, which is based on 3 years of what I've actually listened to. The Last.fm radio is cool and everything, but it would be fun to have this alternate way to browse recommendations more deliberately. Though with so many more recommendations, this design would probably get unwieldy, so you'd have to work out some way to just examine specific parts of the network at a time. E.g. limit it to friends, or neighbors, or tags, or using the obscure/popular slider.