Just to butt in real quick . . .
As for the argument over dimensions or universes, i think it is pretty obvious what someone means when they say alternate dimension. Let's not nitpick. Unless by alternate universe you mean another universe that is physically far away from here but i thought the universe included everything.
The missing word is parallel. Par and several other people have used it, so you all mean the same thing. It's parallel universes though.
And check out some stuff by Michio Kaku and superstring theory. Superstring doesn't directly relate to this (though dimensions-wise it does), but it's interesting nonetheless, and Michio has written extensively on multiple dimentions/parallel universes, though how many of these are online is unknown to me.