GUEST,bankley suggested some songs that certainly don't praise drugs.
Heroin, as sung by the Velvet Underground, may qualify, but it sure doesn't make me want to try it.
Sam Stone is anything but a song praising drugs. It's an anti-drug song if I ever heard one.
Oxycontin Blues isn't a praise of Oxycontin either.

Some of these songs mentioned by other folks also don't answer the request of the original poster. Buffy St.Marie's Codine is not a praise of the drug, nor is Cocaine. It's not too hard to find songs that mention drugs or even songs that are about drugs, but the original poster wanted songs that PRAISE drugs.

It seems to me that I recall a James Taylor song, before he got sober, called Mescalito. It was a song praising the drug and his backing musicians made him put a disclaimer in the liner notes stating that the other musicians on the album did not necessarily agree with the sentiments expressed in the lyrics of that song.