Professor David Nutt has just been sacked as the government's drugs advisor.It seemed he favoured scientific facts over political expediency.
I haven't managed to find his full ranking of drugs danger but the article I've linked to contains this snippet:
"Alcohol ranks as the fifth most harmful drug after heroin, cocaine, barbiturates and methadone. Tobacco is ranked ninth. Cannabis, LSD and ecstasy, while harmful, are ranked lower at 11, 14 and 18 respectively"
So be careful out there!
EDIT: The full report from Professor Nutt is here.