You can check out the trailer here or below.
Keep in mind that Halo: Combat Evolved Anniversary will be using Halo: Reach as its competative Multiplayer mode, so if you're interested in these classic map remakes but don't want to pick up Halo: Combat Evolved Anniversary they will be available a bit down the road as a map pack for Halo: Reach. No word on pricing for that yet, of course.
IGN also has exclusive walkthrough videos for both the map remakes of "Damnation" and "Beaver Creek," which is another fan favourite of old.
Those can be checked out here and here respectively.