TailRank, The Long Tail?
TailRank seems to promise what I was trying to do with the Long Tail of the Blogosphere site, in that it tries to help you discover long tail content.. but the content it shows you is sorted by the number of incoming links. Entries with no incoming links don't seem to show up.
What makes the long tail the long tail, is that it's the content that people haven't discovered and haven't linked to. Showing only content with incoming links certainly increases the quality of the links you see - you're only seeing posts that have been pre-screened, after all - but means you're still closer to the head than the tail.