I won't post the photos here - but drop over to wired & admire the stunning spider images from photographer Nicky Bay. I think my favourite would have to be the Mirror Spider (Thwaitesia sp.), which looks as though it's got a disco ball for an abdomen.
And for awesome mimicry, take a look at the Ant Mimic Jumping Spider (Myrmarachne plataleoides). In fact, I liked this one so much I went looking for more & found this video of a related species:
Looks like an ant, right? But on close inspection there are some clues that all is not as it first appears: surely there are too many legs? And then the 'ant' starts to open & close its 'jaws' & suddenly you see its wickedly sharp fangs and then its pedipalps. How cool a disguise is this?