WhereToWatch is out to change that. Initially announced last year, this site offers a comprehensive search engine of legit sources for movies and tv shows. It's basically the search engine which one would expect Amazon to have built into IMDb (but did not, so far as I can tell).
I've been playing with the site for a few minutes, it does offer a comprehensive set of listings - with a few exceptions. WhereToWatch can't show you the tv listings which might tell you where a movie or show is also playing right now. I also didn't see any mention of Youtube, which does host some full length movies. And I didn't see any entries for Redbox, which may or may not be a bad thing.
In addition to the search results, the site also offers some behind-the-scenes footage from fellow MPAA site thecredits.org. There's also an option for watching trailers, but that didn't work for any of the movies I searched for.
All in all, this is a better search engine than the one Disney would like to build. That one would try to send you to sites owned by a studio's marketing dept rather than review sites, Youtube, and other sites which would help you decide if you liked a movie or book.
Speaking of which, WhereToWatch isn't bad in its current form (although the interface is clunky) but it could use more links leading to reviews and other content about the movie or tv show a user is searching for. This would help users decide if they like a work enough to buy, rent, or stream it.