Though it's a much-requested feature, it's not yet known if we'll see ladders ranking characters in Diablo III.
In Diablo II there are ladders that rank characters by experience. These are sorted by character class, Hardcore and Softcore characters, and by realm. There have been numerous ladder seasons since Diablo II was released, and since D2X these ladder resets have been used to reset the player population and economy, since ladder characters must be created anew in each ladder season, and can only interact with other ladder characters.
Many players would like to see expanded ladders in Diablo III, with more stats tracked and ranked, along with ladders measuring PvP prowess, as well as guilds, and more. Those sorts of features get added very late in the development cycle, or even after release, so it's unlikely that we'll learn more about ladders for some time, yet.