1Up is reporting that Peter Jackson and Microsoft are forming a new games studio, Wingnut Interactive. The announcement cites Jackson's involvement in Halo 3 and a future Microsoft title.

UPDATE: 1Up has added some details to this item, fleshing out Jackson's involvement. It no longer mentions Halo 3 specifically, but does say:

But perhaps more importantly, Microsoft revealed that Peter Jackson will co-write, co-design and co-produce a completely new and original chapter in the Halo universe in collaboration with Bungie Studios. He will also work future title based on an original property from Microsoft.