Sherid found this article in New Scientist, and it's a fine overview of e-smoking. He posted a link in the Chicago Tribune thread, but I think it needs highlighting with its own thread. This is a good intro for anyone relatively new to e-smoking:
Electronic cigarettes: A safe substitute? - health - 11 February 2009 - New Scientist
Electronic cigarettes: A safe substitute? - health - 11 February 2009 - New Scientist