Well, the new Halo 3 trailer has officially been shown during MNF, in case you missed it, I have compiled some links to help out.
Xbox - Trailer and Beta Info
Xbox - Trailer
It is also now available on the Xbox Live Marketplace in 480p and 720p. As of now, those are the only links to the video I could find.
Youtube should have it up fairly soon.
Edit:
IGN - Halo 3 Videos
The first video is the new Halo 3 trailer. It is available in low-res and high-res. The video is apparently named Starry Night. I don't know if this is the official name, or if IGN named this themselves.
New Halo 3 Trailer
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