Any idea where the EXPLODING in space myth originated in Hollyweird? And which movie started that trend?
As with all things in science fiction, it most likely originated in prose at least a decade or two before film and television caught up with it. It probably goes back to early pulp sci-fi stories, from back when people had no direct experience with the vacuum of space and could only speculate about its effects.
Also, it probably comes from a misinterpretation of the term "explosive decompression." We've been conditioned to make certain assumptions about what "explosive" means. It literally means that the gases inside your body or your spaceship will decompress in a single forceful burst through whatever opening is available, but we hear "explosive" and we assume it refers to something blowing up.
Here's a list of films and shows that have used the trope, and those that have averted it:
http://tvtropes.org/pmwiki/pmwiki.php/Main/ExplosiveDecompression
In TNG's "Disaster" they accurately depict exposure to a vaccum when Beverly and Geordi decompress the shuttlebay (to exstinguish a "plasma fire" in the room) Beverly tells Geordi that he may feel some capalaries on his skin burst and that they'd only have a few moments of useful consciousness but otherwise they'll weather the experience nicely.
Except they make a critical mistake: Geordi tells Beverly to hold her breath, which is absolutely the wrong thing to do in that circumstance because you'd rupture your lungs. As a doctor, she should've known better and corrected his mistake before it killed him.