Finally found some numbers to put the "Americans Killed In Iraq" banners I see people holding on the street corners in context.
435,000 Tobacco
365,000 Poor Diet and Physical Inactivity
85,000 Alcohol Related
75,000 Microbial Agents
55,000 Toxic Agents
32,000 Adverse Reactions To Prescription Drugs
30,622 Suicide
29,000 Incidents Involving Firearms
26,347 Motor Vehicle Crashes
20,308 Homicide
20,000 Sexual Behaviors
17,000 Illicit Use of Drugs
7,600 Anti-Inflammatory Drugs
846 Killed in Iraq
0 Marijuana
The numbers are not 1 to 1, death to cause. For example 16,653 of the motor vehicle deaths were alcohol related, and are counted in both 'Motor Vehicle Crashes' and 'Alcohol Related'.
Sources: Iraq numbers, the rest.