I saw a preview of this today and it looked great. It is directed by Sam Raimi (The Evil Dead and the Tobey Maguire's Spiderman's) and stars James Franco, Mila Kunis, Rachel Weisz, and Michelle Williams.
A mischievous magician gains the wisdom to become a powerful ruler after being swept away to a land of magic and mystery as director Sam Raimi and screenwriters Mitchell Kapner and David Lindsay-Abaire (Rabbit Hole) explore the genesis of author L. Frank Baum's enduring tales of Oz. Shady illusionist Oscar Diggs (James Franco) enchants curious audiences at a Kansas circus. Inexplicably transported to the wondrous world of Oz, he encounters three witches named Theodora (Mila Kunis), Evanora (Rachel Weisz) and Glinda (Michelle Williams) who pose him with an awesome challenge: root out a ruinous force of evil that threatens to destroy the entire kingdom, and become the great leader that the population has been waiting for. Should Oscar succeed in summoning the sorcery and creativity to deliver the land from darkness, he will forever be known as the Wizard of Oz.
Here's the preview: