The first white spider I've seen, this unidentified arachnid is a crab spider, a member of the Thomisidae family. It may be a Misumena vatia - despite having being found out-of-season in late October, and lacking the markings common to that species. It appears that other species of Misumena and related genera (Misumenoides, Misumessus and Mecaphesa) are limited to other parts of the world, and not being an arachnologist I can't be sure what to call it.
I noticed the curious critter seeming to imitate a flower as it swung from a web attached to my arm. I don't know how it arrived there in the first place, but when - upon being lowered to the ground - it chose not to immediately skitter away, I took this as a request to be photographed.
I hope for my next encounter to have a proper macro lens, enabling better quality images.