Jizo is the Japanese name of the Indian bodhisattvas Kishitigarbha, a 'Buddhist saint'.
Jizo statues are found in many temples in Japan. They often ware a bib, child bonnet or are surrounded by toys. This is because Jizo is considered as the protector of children. Parents who lost a small child worship Jizo to protect their dead child in the other world.
External links :
http://en.wikipedia.org/wiki/Ksitigarbha
http://www.tinyshiny.com/Articles/JizoBosatsuChildlikeMonk.php