A Damn Interesting article on what would really happen to a human body exposed to hard vacuum.
As is true with many subjects, this representation in popular culture does not reflect the reality of exposure to outer space. Ever since humanity first began to probe outside of our protective atmosphere, a number of live organisms have been exposed to vacuum, both deliberately and otherwise. By combining these experiences with our knowledge of outer space, scientists have a pretty clear idea of what would happen if an unprotected human slipped into the cold, airless void.