I remember posting this on a frighteningly similar thread relatively recently:
BBC story
May interest you if you're into the stories behind the news articles
According to that, while alcohol is only just behind Methadone, 4-MTA [Flatliners], Acid, Methylphenidate, Anabolic Steroids, GHB, Ecstasy, Alkyl Nitrate and Khat are all less harmful than weed.
I have nothing to contribute to this thread really. You all know the arguments, I'm sure.