According to a Microsoft job posting on CareerBuilder.com (via Joystiq), the publisher has big plans in store for the Halo universe that'll apparently take it to small places -- including mobile phones.
By the description of the open position, it seems as though Microsoft's intention is to take the Bungie.net and Halo 3 community features and extend them to mobile networks. "We're looking to blend console, web, and mobile to create an immersive Halo world that follows the dedicated Halo fan wherever they go," the job listing reads. "As an engineer on this team, your responsibility will be to deliver a great out-of-game interactive experience that takes the next step beyond the systems found in Halo 3."

The listing further describes the responsibilities as "designing and delivering code for services supporting community applications and game titles," and "building user-facing on-console features such as forums, tournament ladders, media libraries, and integrated mini-games."

There aren't really any more details than that to go on, so it's hard to say exactly what this job listing will lead to. But whatever it is, we got a feeling we may hear a little more about it at E3 in June.