I had a fairly weird 9/11 realtime experience. I had pulled an all-nighter and ended up going to sleep right around the time this all started happening. So I went to sleep blissfully unaware, and then was woken up by my wife. Within 30 seconds of being woken up I learned: "4 planes were hijacked. They were flown into the World Trade Center. The WTC collapsed."
I kept waiting for the punchline, but then realized it wasn't coming...