Aha! I knew it! The Wiccans did it!
LOL!
But: The biggest clue in the anthrax case is one that hasn't been followed up at all, to my knowledge, except for the spurious Wiccan thing -- the threatening letters (15 of them, as I recall), mailed before 9/11, from Indianapolis, to Sean Hannity, Bill O'Reilly, and maybe others in the media. These letters were said to be very similar to the later anthrax-laced letters (or maybe it's the envelopes that are similar; we have very few details on this).