Movie-Censorship.com has published a handy frame-by-frame comparison of the differences between the two extant versions (they call them US trailer and Canadian trailer, but we like Version 1 and Version 1.1. Whatever.) of the theatrical trailer for The Hobbit.
As you’ll recall, the second version was modified to be more suitable for children so it could be shown attached to films such as Pixar’s Brave.
Thanks to Ringer TheHutt for the heads-up. And, remember, the new trailer is coming in September!