This one's not that silly, but it's really useful: http://labs.google.com/sets
OK, stupid question here: just what would one use it for?
Finding other examples of similar items where you can't quite put your finger on what they have in common, or don't know what the genre is called.
I typed in a couple of titles of movies that I liked, and got a short list of other movie titles. All of them were ones that I am (or had been) vaguely interested in seeing.
It did not do as well when I typed in a few titles of my favourite surf guitar tunes.