The Halo 3 "memorial" diorama site is just an amazing piece of work:
There's also a "making of" video that is told from the perspective of a post-Halo 3 world:
While I'm not completely sure how I feel about the campaign overall, in terms of the realism they're going for, I have to say I am really impressed with the lengths that the team responsible is going to to make the story immersive. The diorama site is engrossing, and definitely draws one further into the story. And the making of video is equally impressive in terms of hitting the right notes while staying within the Halo universe.
What do you all think? Is the pre-launch campaign too much? Just right? Have you pre-ordered your copy yet?