A little more on Mr. Jackson's involvement - from scifiwire (note: article has a few things already mentioned, but offers a few more details which I've highlighted in bold)

I do expect this to be THE big movie of summer 2007

Peter Jackson, who directed of the Lord of the Rings trilogy and the upcoming remake of King Kong, will serve as executive producer of the upcoming film based on Microsoft's blockbuster Halo video game, according to The Hollywood Reporter. Jackson's wife and partner Fran Walsh, who served as writer and producer on his previous films, will co-executive-produce under the team's WingNut films banner. Jackson's New Zealand-based Weta companies will also provide creatures, miniatures and visual effects for the production.

Universal Pictures and 20th Century Fox, the companies behind the project, hope to be in production in the spring with an eye toward a summer 2007 release, the trade paper reported. Prior to Jackson's involvement, Microsoft hired Alex Garland (28 Days Later) to write the screenplay and will have its own consultants on the production, along with the game's developer, Bungie Studios. An announcement about the film's director is expected soon.

"As a gaming fan, I'm excited to bring Halo's premise, action and settings to the screen with all the specificity and reality today's technology can provide," Jackson said. "Fran and I are intrigued by the unique challenges this project offers, and we're delighted to be working again with our friends at Universal, and with our new ones at Fox and Microsoft. I'm a huge fan of the game and look forward to helping it come alive on the cinema screen."

The movie will be shot entirely in the New Zealand capital of Wellington, with a budget of more than $100 million, the trade paper reported. Universal Pictures will handle domestic distribution and Fox will distribute internationally.