Of Shaman King fame, here's another series by Hiroyuki Takei about a buddha with the 1,000 arms armor. Sennju, an emissary of the buddha Kannon, appears in the human world to find and protect the reincarnation of the buddha Mirokou. The emissary arrives on Earth just in time to save a young girl from being bullied by some rough looking men. Just who is this girl and will she believe that he's a buddha who was sent by Kannon?
(Source: MangaCity)

Funbari no Uta is a series of short stories written by Hiroyuki Takei relating to his manga series Shaman King; and a furyoku-inducing battle anthem-turned-jingle-turned-Japanese ballad created by the Shaman King character, Faust VIII.
Funbari no Uta is set seven years later (2007) after the Shaman Tournament, and revolves around Hana Asakura, the son of Yoh and Anna. Hana and Ryunosuke Umemiya are searching for the members of Team Ren and Lyserg for the grand opening of Funbari no Onsen, which is run by Tamao in the story.
(Source: MU)

The Red Crimson begins to target the Tao Family and kicks off the final war for the Tao Family!

The first official spin-off series for Shaman King by Jet Kusakura taking place after the events of the original Shaman King series.

In medieval Japan, a bell hanging on the collar is a sign that a cat has a master. Norachiyo's bell hangs from his katana sheath, but he is nonetheless a stray—a ronin. This one-eyed cat samurai travels across a dishonest world, cutting through pretense and deception with his blade.

(Source: Kodansha Comics USA)

The sequel to the Shaman King and Shaman King Kang Zeng Bang series. Takes place 10 years after the end of Shaman King Kang Zeng Bang and focuses on the life of Hana in his teenage years.

A new collection of short mangas (3-7 pages) printed in the back of the Shaman King Remix Editions (Reprint editions). Each story takes a closer look at a side-story not in the original (or KZB) edition of the Shaman King. Because of their humorous nature, the "plot" of these shorts should not be taken seriously in the series' proper storyline.

New series by Hiroyuki Takei and a sequel to the series Shaman King Flowers. The chapters are serialized in Shonen Magazine Edge magazine.

Yoh Asakura is a shaman--one of the gifted few who, thanks to training or natural talent, can channel spirits that most people can't even see. With the help of his fiancée, Anna, Yoh is in training for the ultimate shaman sports event: the "Shaman Fight in Tokyo," the once-every-500-years tournament to see who can shape humanity's future and become the Shaman King. But unfortunately for Yoh, every shaman in the world is competing for the same prize…

A collection of oneshot stories relating to various Shaman King characters. This is an on-going series, with new chapters being released infrequently. Each chapter is not officially numbered, but the chapter number relate to the order they were released.

The beginning of chapter 6 and the end of chapter 7 connect to after Shaman King Flowers chapter 18 (may contain some spoilers for that series).

Shaman King Kang Zeng Bang is a reprint of the original Shaman King series but with differences including the addition of new chapters (which changes the chapter numbering)