Spock may be dead, but:
FRODO LIVES!!
-Kevin
Is that a serious question? To put it briefly, Spock died at the end of Star Trek II: The Wrath of Khan but mind-melded his brain with McCoy so that he could come back in Star Trek III: The Search for Spock.
Someone correct me if I'm wrong, but the only other one we've "seen" die in subsequent "episodes" is Kirk in the Star Trek: Generations...right?