IGN.com has a great interview posted called Halo 3: In-depth Bungie Q&A in which they talk with Jaime Griesemer and Tyson Green about different aspects of the forthcoming game. Another article recently posted is Halo 3: Beyond the Beta in which they detail some of Halo 3's multiplayer maps and some of the new additions to the Halo universe such as tech and vehicles.
Over the past few days Bungie has released a ton of new renders and Screenshots for Halo 3. The images posted are big at 3840 x 2160 allowing you to see some great details. I have reformatted four of the images, one from each level, available at Bungie.net and posted them below. These images are just a few available for the four different multiplayer maps and one new vehicle, the Brute Chopper, at Bungie.net: