I’m very fond of “You Don’t Know How It Feels” by Tom Petty.
That’s by far the best acid song, but for opiates my favourite is Cod’ine by Buffy Sainte-Marie.
(Visualize an old Delta-blues singer pounding on the guitar - chang CHANG, chang CHANG …)
"My belly is cravin’, got a shakin’ in my HEAAAAD.
I feel like I’m dyin’ and I wish I was deaaaad.
If I live till tomorrow it’ll be a long tiiiime,
But I’ll reel and I’ll fall, and I’ll rise on cod’ine.
*Chorus:*And it’s real, and it’s real, one more time."
(chang CHANG)
I’ve got the following playlist on my iPod, under the title “Bad Influences”
Smoke Two Joints - Sublime
Bong Tokin’ Alcoholics - Kottonmouth Kings
Blood and Whiskey - Dropkick Murphys
Beer - Reverend Horton Heat
A Final Hit - Leftfield
One Toke over the Line - Brewer and Shipley
Bales of Cocaine - Reverend Horton Heat
Drug-Stabbing Time - The Clash
Dope Nose - Weezer
Alcohol - Bare Naked Ladies
Opium - Marcy Playground
Drug Ballad - Eminem
Hits from the Bong - Cypress Hill
Drugs - Talking Heads
Poppies - Marcy Playground
Soma - The Strokes
So High - The Kottonmouth Kings
Strange Brew - Cream
Stoned - Smash Mouth
Fred Eaglesmith (alt country?) - Codeine
Novacaine for the Soul - Eels
Drug Buddy - The Lemonheads
Fixing a Hole (?) - The Beatles
She Said She Said - The Beatles
Catnip Dream - Shonen Knife
No subtext here, just a hard-rockin’ drug song for cats.
How about Sunday Morning Coming Down by Johnny Cash (and written by Kris Kristofferson)?
Also, are we excluding songs about alcohol, tobacco, and caffeine from this thread? Because, if we aren’t, that would add dozens (if not hundreds) of songs.
Ooh, how could I forget Rehab by The Negro Problem?
Pretty much anything off the album “Spanker Madness” by the Asylum Street Spankers. Songs include:
High as You Can Be
Wake and Bake
Gettin’ High
It’s a really fun album.
Cab Calloway’s Minnie the Moocher.
Or, Harry Gibson’s more light-hearted Who Put The Benzedrine In Mrs. Murphy’s Ovaltine?
Sonny Bono – Pattie’s On A Bummer Now
Dillinger – Cocaine In My Brain.
I think Donovan’s version kicks Sainte-Marie’s ass. 
Not off the same album (I think,) but don’t forget “Funny Cigarette.”
Two I haven’t seen mentioned…
-
A Passage to Bangkok* ** Rush **
-
Am I High ? * ** Asleep At The Wheel **
I gotta wonder: What’s the best drug song… for what? For singing about reality? For advocating drug abuse? For advocating getting clean? What exactly do you mean by “best”?
Regardless, I second the nomination for H, by Tool, mostly because the first time I heard it, I couldn’t decide if it was about a dysfunctional love affair or drug addiction. Then I looked at the title on the liner notes and realized it was about a dysfunctional love affair with a drug addiction.
My second nomination is Marijuana by Rev. Horton Heat.
One Toke Over The Line–Brewer & Shipley
One toke over the line sweet Jesus
One toke over the line
Sitting downtown in the railway station
One toke over the line.
Waiting for the train to take me home sweet Jesus
Hooooping that the train is on time.
Sitting downtown in the railway station.
One toke over the line.
Feel Good Hit of the Summer by Queens of the Stone Age
C-c-c-c-cocaine!
Just thought of some more.
Cindy’s Cryin’ by Tom Paxton
Carmelita by Warren Zevon
Too High by Stevie Wonder
Cure for Pain by Morphine
…and I don’t think anyone has mentioned Casey Jones by the Dead.
Say, I may need an audio intervention. My music library appears to be chock a block with these things.
You gotta be high to listen, if not, to even sing this song.
Oh stewball was a racehorse, and I wish he were mine.
He never drank water, he always drank wine.
His bridle was silver, his mane it was gold.
And the worth of his saddle has never been told.
Oh the fairgrounds were crowded, and stewball was there
But the betting was heavy on the bay and the mare.
And a-way up yonder, ahead of them all,
Came a-prancin’ and a-dancin’ my noble stewball.
I bet on the grey mare, I bet on the bay
If I’d have bet on ol’ stewball, I’d be a free man today.
Oh the hoot owl, she hollers, and the turtle dove moans.
I’m a poor boy in trouble, I’m a long way from home.
Oh stewball was a racehorse, and I wish he were mine.
He never drank water,he always drank wine.
Smoke thet Cigarette by Sammy Davis, Jr.
Crumblin Weed OutKast
Go Ask Alice Jefferson Airplane
Insane in the Brain Cypris Hill