From this excellent blog post from the always great Priceonomics blog, it actually followed up this equally great post ranking each city by proportion of race.
To me, even though it's a late entrant, this is probably my favorite data visualization of 2014, for two reasons: it succeeds in its primary purpose of showing which cities are more diverse (those with relatively equal bar lengths by race) and you can also clearly see just how much MORE diverse some cities are than others. So not only could you guess with the numerical value of each percentage but you also get a feeling for the intensity of the diversity as well.