According to this link (which cites canon sources): The crew of the second Death Star is 485,560.

This link (which may not be canon) puts the crew of the first DS at 322,951

UPDATE

And if I'm reading this correctly: The Death Star Technical Companion (PDF) states the crew is 265,675 AND puts the passengers at 607,360!

And to complicate matters even more: I believe in one of the books, someone asks Luke how may people he killed on the first DS and he said about 1 million. Obviously, he felt very guilty about that.

So, the Death Star Technical Companion, if accurate, is more in line with Luke's statement that he killed about a million people! (Assuming everyone was on board)

Therefore, (assuming they were all on board) we're looking at anywhere from approximately 1.3 to almost 1.5 million people killed (at the very least).