Here's the E3 trailer for Halo 3!
http://www.bungie.net/News/content.a...=ethreeblowout
They also got a video called "Arms Race" up there which I've heard is pretty impressive (at work, network is slow today so haven't seen anything yet
)
QuickTime versions over at HBO:
http://nikon.bungie.org/misc/h3_e3_2007/