Over the years I have noticed the clapping getting less frequent as more people get used to flying, but it did happen on a flight into LHR a couple of years ago.
Visibility was practically zero and the cloud was so low you could not see the runway until you landed on it. As we did so, a round of applause broke out.
Being a natural cynic, I said to the person next to me: "If I really believed the pilot landed the aircraft, I'd want to have a go at him for being so reckless, not clap him! I damn well hope the computer did it!".