MSR had a prototype application called "Stuff I've Seen" [1]. It was pretty neat - it would index your browser history (along with other stuff). I don't know what happened to it, but I'm guessing that it eventually ended up being part of Windows Desktop Search. I liked the idea that if I remember seeing something earlier, that this tool would find it.

[1] http://news.cnet.com/2100-1012-997350.html