Peter Watts’ Vampire Lecture
Peter Watts, he of the Blindsight novel I gushed about earlier, has a very amusing and also terrifyingly plausible PowerPoint presentation on evolutionary and biological roots of vampirism, as detailed from the point of view of a scientific researcher whose company is aiming to resurrect (heh) vampires in the present day. If you’ve got about 40 minutes to kill, you might want to check it out (flash required). This iteration of vampirism, incidentally, is the one that is present in Watts’ Blindsight. I found the explanation for the aversion to crosses particularly interesting.