Number dead as a result of 2001 September 11 Hijackings: 2,973
Number dead as a result of Iraq War: 65,000+
Number dead as a result of Traffic Accidents in US in 2005 alone: 43,443
Update 2006-09-18: Ryan Singel says it much better here:
With that in mind, here's a handy ranking of the various dangers confronting America, based on the number of mortalities in each category throughout the 11-year period spanning 1995 through 2005 (extrapolated from best available data).