Let's go get Stoned, 1966 Ray Charles
YouTube description: "Let's Go Get Stoned is a 1966 number-one R&B hit recorded by music legend Ray Charles, and was written by Ashford & Simpson and Joey Armstead. The single was released shortly after Charles was released from rehab after a sixteen-year heroin addiction. It's notable for it being one of Ashford & Simpson's first successful compositions together; the duo also penned Charles' "I Don't Need No Doctor" before they signed with Motown Records working primarily on duets for Marvin Gaye & Tammi Terrell."
I wrote about another classic 420 friendly song, "One Toke Over The Line" previously: http://guydads.blogspot.com/2011/04/420-friendly.html