Sharon Nelson

A Colorado woman, had her lover Gary Adams murder two of her 
three husbands, one in 1983 and one in 1988. 
Book: "The Confessions of an American Black Widow" by Gregg Olsen

http://www.amazon.com/exec/obidos/ASIN/0312965036/102-1441172-7175322

http://www.trinidadco.com/stories98/news/06/23/widow.html