Gotta quibble about the Rolling Stones' "Brown Sugar" that somebody mentioned--*not* a drug song, but a (very blatant)song about sex with black girls.

As far as "positive" songs about non-alcohol drugs, I thought of one or two that haven't been mentioned yet.

The Ramones--"I Wanna Be Sedated"
About, well, sedatives...!

Jim Stafford--"Wildwood Weed"
"We thought it was kinda handy, take a trip and never leave the farm!"

Tom Petty-- "Mary Jane's Last Dance"
Silly me, I thought this one was about a girl but my kids assure me to the contrary. It doesn't strike me as a particularly cheery song, but its message is certainly more on the pro-pot than the con-pot side of things.

Pink Floyd--"Comfortably Numb"
Again, whether or not this is pro-drug is debatable. The narrator is being drugged out of his gills by a doctor so he can make it through the next show. I think it sounds more negative, but the narrator claims to be "comfortable."

Jefferson Airplane--"Go Ask Alice" (Also known as "White Rabbit")
I am going to respectfully disagree with the person who classified this as a con-drug song. Sorry, but the ending line: "Feed your head!" in context cannot be heard as anything other than a ringing endorsement.

I could probably dredge up a few (quite a few!) more, given my fondness for the music of the 60s & 70s when I'm not listening to folk songs and sea shanties. But I'll just mention a couple of things: the late and much lamented Bob Kotta's "Tequila in the Jar" contains the line "Marijuana no fumar" but I have also heard it sung "marijuana si fumar." And am I the only one who remembers that Donovan's "Mellow Yellow" sparked a fad for smoking banana peels, in the belief that they would get you high?

As to why alcohol is so celebrated in song, as opposed to other substances, I see a couple of factors at play. One is simply that booze has been around longer. That's not to say that our caveman ancestors weren't out smoking the meadow or snacking on the local mushrooms--they may well have been. But there is evidence that our Neolithic ancestors were brewing or fermenting alcoholic beverages. The ancient Egyptians certainly were. By the Middle Ages, ale or wine were common features at mealtimes, and in many places that is still the case. The same cannot be said for other recreational drugs.

Along with that--and related to it--is simply the fact that alcohol is much more socially acceptable. Obviously, if music of any genre concerned itself only with things that are legal, our musical traditions would be much less interesting and fun! Still, alcohol use (and abuse) being a part of daily life for the last 6,000--9,000 years it would probably be more surprising if it *didn't* show up in song. Even before things like opium and marijuana and cocaine were made illegal, they were much less commonly or openly used. And I think that may have something to do with why those substances turn up less frequently in songs, and especially less often in a positive light.

That's my 15 minute, off-the-cuff take on it, anyway. YMMV.