TIGTIDAW #130 - White Crab Spider
This shot was sent to a co-worker, and hence to me, for ID. It's a female Thomisus spectabilis, a common Australian species that ambushes anything that visits the flower it's sitting on. This includes successfully killing other spiders, bees, or butterflies much much bigger than themselves. This genus of Crab Spiders is found over most of the world, with the odd exception of South America.
Males can be a variety of colours, but usually yellow, and the female can adjust her colour to match the flower she's on. See here for examples, and wonderful close-ups.