I would love something like that; unfortunately for whatever reason people seem hellbent on thinking that book people are not movie people are not music people. I did a search on Emily's site and came up with this: http://www.emilychang.com/go/search/results/48c63e6813b0400667c57e5044025955/ - I warn you though I briefly glanced through and it doesn't look like most of the projects have that many users.

I assume you are talking about LibraryThing for books; it's a really good product - they even have an UnRecommender tool - where you plug in say, Harry Potter and it gives you the opposite.

http://www.douban.net/ might be along the lines of what you're looking for - has music and books but not movies.