Starting on October 25th, the original Shaman King anime will be shown on the Animax channel in Japan. The anime originally was produced in 2001. Each episode will be shown 3 times each day and proceed with a new episode each day. Currently the schedule only lists the first 12 episodes on their website.
Currently the original Shaman King anime is Out of Print (OOP) on DVD and VHS. The series was never released on Blu-Ray (or HD-DVD or LaserDisc or BetaMax). The is no current digital options to purchase the series.
Series main page: http://www.animax.co.jp/program/NN00015249
TV Schedule: http://www.animax.co.jp/program/NN00015249/schedule1
*EDIT : Schedule is currently listing up to episode 26, airing on November 29th. More episodes expected after that!
10/10 Update:
Animax has also created a special Shaman King promotional website, you can find here. This showing isn’t really a precursor to a “new Shaman King anime.” This is just a marketing campaign that is jointly funded between Animax and JumpKai to help cross-promote the anime and the manga series. That’s why there is prizes and a full color ad in the latest Jump Kai issue. Still nice to see the Shaman King anime be back in the spotlight for a little bit, even if it’s just marketing.