VX is a nerve agent. It is a colorless, oily liquid. <1 drop can be lethal. It can be inhaled or absorbed through the skin. It could be manufactured by terrorists if they had the $$ and a few well schooled organic chemists on staff. The doomsday yahoos in Japan used a homegrown variety of nerve agent in a subway (read confined space) and were only marginally successful. I guess the short answer is yes, it could be done but the odds are pretty long against it. The government does a pretty good job of monitoring who's buying precursor chemicals. If the average schmuck starts buying all of the neccesary ingredients for VX on a Visa card, said schmuck can probably expect a knock on the door from one of the TLAs (three letter agencies <img src="images/graemlins/wink.gif" alt="" />)
Bear in mind, the media loves scare the bejesus out of people with real or imagined threats. It keeps us glued to the idiot box and they make more money. Your average 6 year old can't blow up a federal building with finger paint and bubble gum, 99.9% of high school students don't carry a gun, and and it's a lot harder to cook up anthrax or VX in your kitchen than Diane Sawyer were ever let on.

Ed

(Sorry about going off on a tangent there. Sometimes the soapbox is just too tempting <img src="images/graemlins/cool.gif" alt="" />)