Jim’s Son asked the question in this Hendrix thread but nobody responded so I thought it deserved a thread of its own.
Off the top of my head, the biggest posthumous response was after John Lennon’s death, when “Women” was a huge hit and “Watching the Wheels” a decent-sized one. The Double Fantasy album had been released only three weeks before his death and it sold several extra million because of it.
“It Doesn’t Matter Anymore” was released a month after Buddy Holly died. It hit #13 but is played more than his last few pre-death singles today.
“Riders on the Storm” didn’t hit the Hot 100 until the day that Jim Morrison died and eventually went to #14, all of that after his death. “L. A. Woman” was never an official single but I’d have to argue that its continuous airplay was a result.
What else do you have?