Peter Jackson will be producing. Ian McKellan has already confirmed he'll be back as Gandalf the Grey, and Andy Serkis will once again play Gollum. Should any other characters from the LOTR trilogy appear in The Hobbit, most cast members have expressed interest in returning as well. Some reasonable characters to return could be Saruman, Arwen, Legolas, and Aragorn.
Del Toro has said he would be interested in having Ian Holm reprise his role as Bilbo, but if it should be decided he's too old, James McAvoy has been rumored to play the role.
As of now, the movie is in pre-production, and is being planned as a duology, with the first film being a straight adaptation of The Hobbit, and the second being a bridge between The Hobbit and the LOTR trilogy.
--I figured I'd get the hype started early. I have every intention of TTTing this in 2011.
I'm sure we'll have plenty of updates before then. Meantime, here's some good links.
http://the-hobbit-movie.com/
http://www.theonering.net/
http://www.councilofelrond.com/
http://www.imdb.com/title/tt0903624/
UPDATE 8/14/08:
Just a few bits of information taken from hobbit-movie.com ---
James McAvoy says he won't be Bilbo.
Ian Holm won't play the leading part in The Hobbit, but should have some other small role (maybe older Bilbo in a flashback).
Del Toro clarifies there will definitely be two movies.
Del Toro will write the screenplay for the first Hobbit movie. Jackson, Walsh and Boyens for the second movie. Then they plan to switch and rewrite each other.
Howard Shore, who composed the music for Lord of the Rings, will be composer for The Hobbit, too.
UPDATE 12/1/08:
So GDT has announced an official start to shooting in 2010, and we should expect an announcement on Bilbo soon...
http://www.movieweb.com/news/NEEuDFGIuonRIJ
UPDATE 3/9/09
Empire article [and cover] on The Hobbit.
http://www.empireonline.com/news/story.asp?NID=24081
UPDATE 10/16/10
The two films have been officially greenlit, with filming to start in February 2011. Martin Freeman is strongly rumored to have accepted the role of Bilbo.
UPDATE 3/4/11
Filming finally starting on March 21st. And we have a title!
UPDATE 3/21/11
It's been a long time coming, but The Hobbit production is OFFICIALLY underway! Check out the official Hobbit blog here.
UPDATE 7/31/12
Pretty major update needed:
Although filming had ended a couple of weeks ago, it's now confirmed that there will be THREE Hobbit films, with the third coming summer of 2014. This most likely means there will be additional filming to be done. There's no way of knowing how exactly this will affect the first film, if at all. In any case, just four and a half months to go until film one!
Release Schedule:
The Hobbit: An Unexpected Journey - December 14, 2012
The Hobbit: The Desolation of Smaug - December 13, 2013
The Hobbit: There and Back Again - July 18, 2014
[This message has been edited by sharkenleo (edited 9/2/2012 7:57p).]
[This message has been edited by sharkenleo (edited 10/23/2012 5:58p).]