Many of the more progressive scripture scholars speculate that 666 is the numerical value of the name of "Neron Caesar" (Nero), who was notorious for his persecutions. I do like Jon's "Rupert Murdoch" speculation, however. Progressive theologians tend to see the Book of Revelation as written primarily for first-century Christians who were facing Roman persecution. Progressives see the apocalyptic writings as also having meaning for all time, since we all face cataclysmic, "apocalyptic" events in our lives. Evangelicals tend to see the Book of Revelation and other apocalyptic writings as predicting the imminent but future end of the world. Progressives don't usually buy into predictions, although they can see value in predicting the logical consequences of actions. "Apocalypse," by the way, comes from the Greek word meaning simply "lifting of the veil" or "revelation."
I added a bit to the thread title because chances are good that nobody is going to know who the hell Harold Camping is, once his 15 minutes of fame are up. I thought they were up at the end of the day on May 21, but I see that he has found a way to extend his time a little longer.