TBF, I think you'd run out of air first
But seriously, from what I remember reading (and this was years ago) a person won't freeze or boil instantly in a vacuum. I think that you dry out pretty quick because any liquid (from eyes, nose, mouth and the skin) boils off, so you essentially get flash frozen. It's not all that fast though, and it's not due to temperature changes, it's because of the low pressure. Remember pV = nKT; counter-intuitive things happen at weird pressures and temperatures. That's how cloud chambers [http://en.wikipedia.org/wiki/Cloud_chamber#Structure_and_operation] work.
The other thing that was thought to be potentially dangerous about being in space without a suit was actually sunburn. The suns light is an awful lot stronger outside of the atmosphere, which is why astronauts have those funny gold visors, and it could blind you (or possibly overheat you) if you were caught out of the shadows.
Without the sun temperature doesn't really play a part though. The liquids boiling off you would keep you cool enough in the short term to counteract the insulative properties of a vacuum. When you run out of liquids, you get very hot, but there's nothing left for the heat to boil.