Realm Pop shows you population statistics on the players' characters in World of Warcraft.

You can find out the most popular races and classes on your realm, or across all realms, or across a subset of realms that you choose (for example, PvP realms, or Oceanic realms). On realm pages, with each subset you choose, you will also get a partial list of characters so you can look them up on the Armory.

Find it here:
http://wow.realmpop.com/

Do we have a thread here that lists API apps? I'm curious to find apps I've missed. There's obviously a bunch of us here, but I don't hear much about the apps that get produced.