Quicksilver Messenger Service - Happy Trails (Roy Rogers & Dale Evans)
Tomita - Pictures at an Exhibition (Mussosky/Various Artists)
The Force - Star Wars Disco (John Williams)
Manfred Mann - Blinded by the Light (Bruce Springsteen)
Honorable Mention:
Fraternity of Man - Don't Bogart that Joint (Okay, maybe there wasn't an earlier version, but the chances of these lyrics being sang, hummed, slurred, or st-st-st-studdered by the Flower People in the Bay Area after a couple of "hits" in the 60's was a certainty)
Doobie Brothers - Black Water (First sang by Bob Winnebago in 1966 as he was dumping the sewage tank on his first RV)