Some time ago, I created a little addon to Last.fm called Music Intersector. It shows which bands are common between the favorites of two users. As you might have noticed, Last.fm has integrated this functionality into its own system, so my old music intersector became a bit pointless.
Not anymore. I just updated it and it can now show the musical similarities between up to five users. Perfect for small parties and gatherings. :)
Unfortunately, the number of results declines extremely rapidly with more than two users. There is not much that I can do about it, since Last.fm only offers access to the top 50 artists and not the whole profile.