FindTheBest.com allows a user to make some interesting, side-by-side comparisons of just about anything.
I found the site's data-pull and comparison regarding classic literature to be interesting enough that I will probably go back to the site to see what else is there. Take a look here if you're curious. While the comparison does not go into great depth, there is enough there to make it a useful tool. I imagine that the retail product comparisons would be especially helpful but, hey, this is a book blog.
Here's another one, this time comparing the libraries of major cities around the world by number of printed books, e-books, audio materials, etc. The size of some of these libraries is amazing, but what surprises me most is the identity of some of those with the largest collections.