I was having a discussion about what would happen to you if you were exposed in deep space (ie without a space suit). There are a few considerations for what would happen. This sort of event happens a lot in space movies, but the film industry doesn't really have a clear vision. The things I came up with to worry about are:

1. ~0 atmospheres of pressure
2. very low (like, a few kelvin) temperatures
3. radiation

so what really would happen? My guess is that the zero atmospheres of pressure would do you in first. Your innards would probably come exploding out of your body, and those that couldn't get out would just pop.

Of course, freezing isn't too healthy either. And if you live through that, the X-rays and such would probably be pretty uncomfortable.

Here's the simile I came up with:

You could compare being in deep space to floating down the Amazon river on your back with your ass painted red and honey on your belly. It's hard to say what would get you first, but you're pretty much fucked.

So I did some google searches, and i'm pretty much completely wrong. According to info on this nasa page, "If you don't try to hold your breath, exposure to space for half a minute or so is unlikely to produce permanent injury. ... exposure to vacuum causes no immediate injury. You do not explode. Your blood does not boil. You do not freeze. You do not instantly lose consciousness." However, the radiation would be problematic after much of any time.