The ox herding pictures, also known as the nine or ten Bulls of Zen are a story board detailing stages of the quest to master the mind, using the analogy of catching and mastering an escaped, renegade bull or ox. In the analogy the mind is the escaped ox, which must be discerned from his footprints (we become aware of the mind as an entity separate from us by the telltale signs we notice in our life) and so the hunt is on. Later comes roping and riding the thing. It's a great analogy.

For a long time, these images were known as the 9 oxherding pictures. The tenth was kept hidden from students of the path. Just in case they thought they could take a shortcut, and not bother with all the ox catching and bull riding.

There's plenty articles around the web, just search for "ox herding pictures" and "ten bulls of zen".

There's an irreverent, but probably sincere rendition of the traditional theme at osho-holics.com.