Space will not kill you immediately. You will most likely die of oxygen depletion and begin to suffocate. Your body will not explode like most people want you to believe.
A few downsides to space.
- No Oxygen - You will choke to death, so basically as long as you can hold your breath is how long you got. This will be what kills people most of the time.
- No Ozone layer to keep radiation from making contact with your skin - will slowly kill your cells from exposure to gamma radiation, unless you're behind planet or moon.
- Don't have exacts on this statement, but space is very cold. So freezing to death is probably another way to go if left out to long.
Your skin will probably turn red though from your insides trying push out and creating pressure, but your skin and skeleton are more than enough to hold your organs and the rest of your insides...well inside.