Is the vermiculite found in my popcorn ceiling toxic? Can I remove it myself?
Vermiculite on its own poses no health risk, and can be removed without concern.  However, in many cases, mined vermiculite can contain traces of Asbestos, and so its removal is not recommended without an asbestos test.  I would, as Scott suggests, call the testing company, and make sure that since no asbestos fibers were found, this indicates that the vermiculite used was asbestos free.  If that is the case, you are good to go (that being said- wear a mask when you strip the popcorn ceilings, or you'll be coughing and hacking a lot- that dust is nasty).