What kind of rock or stone is this? Where did it come from?
Quite an interesting stone.  I cannot identify all of it but given its location, and the patterns it is primarily Agate, a type of crypto-crystalline quartz.  The fourth picture down shows a layer of lace agate across the top of the stone at that location, it is underlain with a more massive translucent agate.  In the Oregon area there are many areas with volcanic rock.  The silicas have dissolved from the volcanic material in the past and this silca has been slowly deposited to form the rock you found.  The following links give you an idea of the types of agate you can find.  

Types of agate 

A more detailed description of types and formation.

I would warn you that there are a number of names for the various types of agates and the naming doesn't seem to follow any convention.