Now that Aleph One v1.0 is released, I think it'd be really cool for a dedicated person or group of people to do some "let's play"s of the Marathon games.
If you're not familiar with the concept of a Let's Play, it's basically a walkthrough of a game, alongside commentary of some sort. Often a community pitches in their thoughts in a forum thread, sometimes helping determine what game paths are played. See http://lparchive.org for a vast number, in many different styles. Many of the best are performed by true fans of their game, offering very thorough insight into the secrets, tricks, and story.
I know that this story forum has done something similar before in text-based format (with the "Volunteers" section, linked on the main site at http://marathon.bungie.org/story/volunteersseries.html ), with various people playing through a level and commenting with their thoughts. What I'd really love to see is a video playthough of the Trilogy, with the same knowledge of the game and its story conveyed through during-play commentary. A lot of the work done in "Volunteers" could be used as a base, even. I think a youtube series like this could expose many more people to the magic of orbital bomba~, sorry, of the series.
While a couple of video playthroughs do currently exist on youtube, in my opinion they really don't do the game or the story justice. Something produced by one of the vid or loremasters on this forum would be amazing. I think the effort would be worth it. I would start it myself, but my gameplay ability frankly stinks :P